610 research outputs found
A simple footskate removal method for virtual reality applications
Footskate is a common problem encountered in interactive applications dealing with virtual character animations. It has proven difficult to fix without the use of complex numerical methods, which require expert skills for their implementations, along with a fair amount of user interaction to correct a motion. On the other hand, deformable bodies are being increasingly used in virtual reality (VR) applications, allowing users to customize their avatar as they wish. This introduces the need of adapting motions without any help from a designer, as a random user seldom has the skills required to drive the existing algorithms towards the right solution. In this paper, we present a simple method to remove footskate artifacts in VR applications. Unlike previous algorithms, our approach does not rely on the skeletal animation to perform the correction but rather on the skin. This ensures that the final foot planting really matches the virtual character's motion. The changes are applied to the root joint of the skeleton only so that the resulting animation is as close as possible to the original one. Eventually, thanks to the simplicity of its formulation, it can be quickly and easily added to existing framework
Modern middleware for the data acquisition of the Cherenkov Telescope Array
The data acquisition system (DAQ) of the future Cherenkov Telescope Array
(CTA) must be ef- ficient, modular and robust to be able to cope with the very
large data rate of up to 550 Gbps coming from many telescopes with different
characteristics. The use of modern middleware, namely ZeroMQ and Protocol
Buffers, can help to achieve these goals while keeping the development effort
to a reasonable level. Protocol Buffers are used as an on-line data for- mat,
while ZeroMQ is employed to communicate between processes. The DAQ will be
controlled and monitored by the Alma Common Software (ACS). Protocol Buffers
from Google are a way to define high-level data structures through an in-
terface description language (IDL) and a meta-compiler. ZeroMQ is a middleware
that augments the capabilities of TCP/IP sockets. It does not implement very
high-level features like those found in CORBA for example, but makes use of
sockets easier, more robust and almost as effective as raw TCP. The use of
these two middlewares enabled us to rapidly develop a robust prototype of the
DAQ including data persistence to compressed FITS files.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherlands. All CTA contributions at
arXiv:1508.0589
Fermi surface topology and vortex state in MgB2
Based on a detailed modeling of the Fermi surface topology of MgB2 we
calculated the anisotropy of the upper critical field Bc2 within the two gap
model. The sigma-band is modeled as a distorted cylinder and the pi-band as a
half-torus, with parameters determined from bandstructure calculations. Our
results show that the unusual strong temperature dependence of the Bc2
anisotropy, that has been observed recently, can be understood due to the small
c-axis dispersion of the cylindrical Fermi surface sheets and the small
interband pairing interaction as obtained from bandstructure calculations. We
calculate the magnetic field dependence of the density of states within the
vortex state for field in c-axis direction and compare with recent measurements
of the specific heat on MgB2 single crystals.Comment: 2 pages, 2 figure
Influence of ionospheric perturbations in GPS time and frequency transfer
The stability of GPS time and frequency transfer is limited by the fact that
GPS signals travel through the ionosphere. In high precision geodetic time
transfer (i.e. based on precise modeling of code and carrier phase GPS data),
the so-called ionosphere-free combination of the code and carrier phase
measurements made on the two frequencies is used to remove the first-order
ionospheric effect. In this paper, we investigate the impact of residual
second- and third-order ionospheric effects on geodetic time transfer solutions
i.e. remote atomic clock comparisons based on GPS measurements, using the
ATOMIUM software developed at the Royal Observatory of Belgium (ROB). The
impact of third-order ionospheric effects was shown to be negligible, while for
second-order effects, the tests performed on different time links and at
different epochs show a small impact of the order of some picoseconds, on a
quiet day, and up to more than 10 picoseconds in case of high ionospheric
activity. The geomagnetic storm of the 30th October 2003 is used to illustrate
how space weather products are relevant to understand perturbations in geodetic
time and frequency transfer.Comment: 25 pages, 10 eps figures, 1 table, accepted in Journal of Advances in
Space Research, Special Issue "Recent advances in space weather monitoring,
modelling and forecasting
Magnetic field dependence of the coherence length and penetration depth of MgB2 single crystals
International audienceWe report on specific heat and Hall probe magnetization measurements in magnesium diboride single crystals. A magnetic field dependence of the coherence length has been deduced from the former assuming that the electronic excitations are localized in field dependent vortex cores in which case is related to the Sommerfeld coefficient = Cp /T T→0 throughout, H /a0 2 a0 being the vortex spacing . The reversible part of the magnetization has been analyzed with a phenomenological Ginzburg-Landau model introducing field dependent parameters i.e., penetration depth and which account for the decreasing contribution of the -band with increasing field. This approach perfectly reproduces the experimental data by combining the field dependence of deduced from Cp 1/ 2 B with an almost linear increase of from 450 Å at low field to 700 Å close to Hc2. These field dependences can then be used to consistently describe the field dependence of the critical current density, small angle neutron scattering form factor, and muon spin relaxation rate
ALTICORE: an initiative for coastal altimetry
ALTICORE (value-added ALTImetry for COastal REgions) is an international initiative whose main objective is to encourage the operational use of altimetry over coastal areas, by improving the quality and availability of coastal altimetry data. The ALTICORE proposal has recently been submitted for funding to the INTAS scheme (www.intas.be) by a consortium of partners from Italy, France, UK, Russia and Azerbaijan. ALTICORE is also meant as a contribution to the ongoing International Altimeter Service effort.
In this work we will describe the anticipated project stages, namely: 1) improvement of the most widely distributed, 1 Hz, data by analyzing the corrective terms and providing the best solutions, including those derived from appropriate local modelling; 2) development of a set of algorithms to automate quality control and gap-filling functions for the coastal regions; 3) development of testing strategies to ensure a thorough validation of the data.
The improved products will be delivered to ALTICORE users via Grid-compliant technology; this makes it easier to integrate the local data holdings, allows access from a range of services, e.g. directly into model assimilation or GIS systems and should therefore facilitate a widespread and complete assessment of the 1Hz data performance and limitations. We will also outline the design and implementation of the Grid-compliant system for efficient access to distributed archives of data; this consists of regional data centres, each having primary responsibility for regional archives, local corrections and quality control, and operating a set of web-services allowing access to the full functionality of data extraction.
We will conclude by discussing a follow-on phase of the project; this will investigate further improvements on the processing strategy, including the use of higher frequency (10 or 20 Hz) data. Phenomena happen at smaller spatial scales near the coast, so this approach is necessary to match the required resolution. The whole project will hopefully promote the 15-year sea surface height from altimetry to the rank of operational record for the coastal areas
Influence of Al doping on the critical fields and gap values in magnesium diboride single crystals
The lower () and upper () critical fields of
MgAlB single crystals (for , 0.1 and )
have been deduced from specific heat and local magnetization measurements,
respectively. We show that and are both decreasing with
increasing doping content. The corresponding anisotropy parameter
value also decreases from
in pure MgB samples down to for whereas
remains on the order of 1 in
all samples. The small and large gap values have been obtained by fitting the
temperature dependence of the zero field electronic contribution to the
specific heat to the two gap model for the three Al concentrations. Very
similar values have also been obtained by point contact spectroscopy
measurements. The evolution of those gaps with Al concentration suggests that
both band filling and interband scattering effects are present
- …