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Geometry videos
We present the "Geometry Video," a new data structure to encode animated meshes. Being able to encode animated meshes in a generic source-independent format allows people to share experiences. Changing the viewpoint allows more interaction than the fixed view supported by 2D video. Geometry videos are based on the "Geometry Image" mesh representation introduced by Gu et al. Our novel data structure provides a way to treat an animated mesh as a video sequence (i.e., 3D image) and is well suited for network streaming. This representation also offers the possibility of applying and adapting existing mature video processing and compression techniques (such as MPEG encoding) to animated meshes. This paper describes an algorithm to generate geometry videos from animated meshes.The main insight of this paper, is that Geometry Videos re-sample and re-organize the geometry information, in such a way, that it becomes very compressible. They provide a unified and intuitive method for level-of-detail control, both in terms of mesh resolution (by scaling the two spatial dimensions) and of frame rate (by scaling the temporal dimension). Geometry Videos have a very uniform and regular structure. Their resource and computational requirements can be calculated exactly, hence making them also suitable for applications requiring level of service guarantees.Engineering and Applied Science
Magneto-Acoustic Waves of Small Amplitude in Optically Thin Quasi-Isentropic Plasmas
The evolution of quasi-isentropic magnetohydrodynamic waves of small but
finite amplitude in an optically thin plasma is analyzed. The plasma is assumed
to be initially homogeneous, in thermal equilibrium and with a straight and
homogeneous magnetic field frozen in. Depending on the particular form of the
heating/cooling function, the plasma may act as a dissipative or active medium
for magnetoacoustic waves, while Alfven waves are not directly affected. An
evolutionary equation for fast and slow magnetoacoustic waves in the single
wave limit, has been derived and solved, allowing us to analyse the wave
modification by competition of weakly nonlinear and quasi-isentropic effects.
It was shown that the sign of the quasi-isentropic term determines the scenario
of the evolution, either dissipative or active. In the dissipative case, when
the plasma is first order isentropically stable the magnetoacoustic waves are
damped and the time for shock wave formation is delayed. However, in the active
case when the plasma is isentropically overstable, the wave amplitude grows,
the strength of the shock increases and the breaking time decreases. The
magnitude of the above effects depends upon the angle between the wave vector
and the magnetic field. For hot (T > 10^4 K) atomic plasmas with solar
abundances either in the interstellar medium or in the solar atmosphere, as
well as for the cold (T < 10^3 K) ISM molecular gas, the range of temperature
where the plasma is isentropically unstable and the corresponding time and
length-scale for wave breaking have been found.Comment: 14 pages, 10 figures. To appear in ApJ January 200
Spitzer Space Telescope study of disks in the young Orionis cluster
We report new Spitzer Space Telescope observations from the IRAC and MIPS
instruments of the young (~ 3 Myr) sigma Orionis cluster. We identify 336 stars
as members of the cluster using optical and near-infrared color magnitude
diagrams. Using the spectral energy distribution (SED) slopes in the IRAC
spectral range, we place objects in several classes: non-excess stars, stars
with optically thick disks(like classical T Tauri stars), class I
(protostellar) candidates, and stars with ``evolved disks''; the last exhibit
smaller IRAC excesses than optically thick disk systems. In general, this
classification agrees with the location expected in IRAC-MIPS color-color
diagrams for these objects. We find that the evolved disk systems are mostly a
combination of objects with optically thick but non-flared disks, suggesting
grain growth and/or settling, and transition disks, systems in which the inner
disk is partially or fully cleared of small dust. In all, we identify 7
transition disk candidates and 3 possible debris disk systems. As in other
young stellar populations, the fraction of disks depends on the stellar mass,
ranging from ~10% for stars in the Herbig Ae/Be mass range (>2 msun) to ~35% in
the T Tauri mass range (1-0.1 msun). We find that the disk fraction does not
decrease significantly toward the brown dwarf candidates (<0.1 msun). The IRAC
infrared excesses found in stellar clusters and associations with and without
central high mass stars are similar, suggesting that external photoevaporation
is not very important in many clusters. Finally, we find no correlation between
the X-ray luminosity and the disk infrared excess, suggesting that the X-rays
are not strongly affected by disk accretion.Comment: 44pages, 17 figures. Sent to Ap
The stellar content of the young open cluster Trumpler 37
With an apparent cluster diameter of 1.5{\deg} and an age of ~4 Myr, Trumpler
37 is an ideal target for photometric monitoring of young stars as well as for
the search of planetary transits, eclipsing binaries and other sources of
variability. The YETI consortium has monitored Trumpler 37 throughout 2010 and
2011 to obtain a comprehensive view of variable phenomena in this region. In
this first paper we present the cluster properties and membership determination
as derived from an extensive investigation of the literature. We also compared
the coordinate list to some YETI images. For 1872 stars we found literature
data. Among them 774 have high probability of being member and 125 a medium
probability. Based on infrared data we re-calculate a cluster extinction of
0.9-1.2 mag. We can confirm the age and distance to be 3-5 Myr and ~870 pc.
Stellar masses are determined from theoretical models and the mass function is
fitted with a power-law index of alpha=1.90 (0.1-0.4 M_sun) and alpha=1.12
(1-10 M_sun).Comment: 9 pages, 10 figures, 2 long tables, accepte
Awareness of nonalcoholic steatohepatitis and associated practice patterns of primary care physicians and specialists
The endoscopic endonasal approach is not superior to the microscopic transcranial approach for anterior skull base meningiomas-a meta-analysis
Scientific Assessment and Innovation in Neurosurgical Treatment Strategie
On Solving the Coronal Heating Problem
This article assesses the current state of understanding of coronal heating,
outlines the key elements of a comprehensive strategy for solving the problem,
and warns of obstacles that must be overcome along the way.Comment: Accepted by Solar Physics; Published by Solar Physic
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