Constraints on cometary surface evolution derived from a statistical analysis of 67P's topography

We present a statistical analysis of the distribution of large-scale topographic features on comet 67P/Churyumov-Gerasimenko.We observe that the cumulative cliff height distribution across the surface follows a power law with a slope equal to -1.69 ± 0.02. When this distribution is studied independently for each region, we find a good correlation between the slope of the power law and the orbital erosion rate of the surface. For instance, the Northern hemisphere topography is dominated by structures on the 100 m scale, while the Southern hemisphere topography, illuminated at perihelion, is dominated by 10 m scale terrain features. Our study suggests that the current size of a cliff is controlled not only by material cohesion but also by the dominant erosional process in each region. This observation can be generalized to other comets, where we argue that primitive nuclei are characterized by the presence of large cliffs with a cumulative height-power index equal to or above -1.5, while older, eroded cometary surfaces have a power index equal to or below -2.3. In effect, our model shows that a measure of the topography provides a quantitative assessment of a comet's erosional history, that is, its evolutionary age. © 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

The 8 Be scattering system in the framework of a microscopic theory

We present conclusions for the 8 Be scattering system from a multi-channel calculation in the framework of a microscopic nuclear cluster model. The energy region from α-α threshold up to 30 MeV center of mass is investigated; results of an eigenphase analysis for J π -values from 0 + to 4 + and 0 − to 4 − are displayed. For comparison and completion we have performed quasibound state calculations taking into account possible combinations of participating structures. The results throw light upon a complicated sequence of resonant states and moreover predict the occurrence of some additional levels in the energy spectrum.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45823/1/10050_2005_Article_BF01408973.pd

Automatic Creation of Flexible Antropomorphic Models for 3D Videoconferencing

This contribution describes the automatic creation of highly realistic flexible 3D models of participants for distributed 3D videoconferencing systems. The proposed technique uses a flexible mesh template surrounding an interior skeleton structure, which is based on a simplified human skeleton. The vertices of this template are arranged in rigid rings along the bones of the skeleton. Using 3D data obtained by a shape from silhouette approach the size and shape of the mesh template is adapted to the real person. Texture mapping of the adapted mesh using real camera images leads to a natural impression. The mesh organization in rigid rings allows an efficient surface deformation according to the skeleton movements. Once the resulting model is transmitted, it can be animated subsequently using the simple parameter set of the interior skeleton structure. Results obtained with real image data confirm the eligibility of the animated person models in terms of realism and efficiency for 3D vid..

How Far Away are We From the Virtual Actor and the Virtual Scene?

This paper discusses 3-D generation techniques in view of virtual actors and scenes. Naturally looking virtual actors and scenes are obtained using current 3-D reconstruction techniques that describe real objects by 3-D models. Four techniques are introduced: For the generation of virtual sets, 3-D models of rigid objects are generated using a shape from silhouette approach. Arbitrary time-varying scenes are reconstructed using a stereo vision technique. When dealing with humans, this knowledge can be exploited for improving the 3-D models. Therefore, modelbased reconstruction techniques for persons are described using body animation for whole persons and facial animation when facial expressions are of interest. The naturalness of these 3-D models is illustrated, and their benefit for movie production is discussed. Keywords: 3-D reconstruction, body animation, facial animation, virtual actor, virtual set, 3-D modelling 1 Introduction Virtual scenes and virtual actors can be seen as s..