9,184 research outputs found
A study of event traffic during the shared manipulation of objects within a collaborative virtual environment
Event management must balance consistency and responsiveness above the requirements of shared object interaction within a Collaborative Virtual Environment
(CVE) system. An understanding of the event traffic during collaborative tasks helps in the design of all aspects of a CVE system. The application, user activity, the display
interface, and the network resources, all play a part in determining the characteristics of event management.
Linked cubic displays lend themselves well to supporting natural social human communication between remote users. To allow users to communicate naturally and subconsciously, continuous and detailed tracking is necessary. This, however, is hard to balance with the real-time consistency constraints of general shared object interaction.
This paper aims to explain these issues through a detailed examination of event traffic produced by a typical CVE, using both immersive and desktop displays, while supporting a variety of collaborative activities. We analyze event traffic during a highly collaborative task requiring various forms of shared object manipulation, including the concurrent manipulation of a shared object. Event sources are categorized and the influence of the form of object sharing as well as the display device
interface are detailed. With the presented findings the paper wishes to aid the design of future systems
Quantum States of Neutrons in Magnetic Thin Films
We have studied experimentally and theoretically the interaction of polarized
neutrons with magnetic thin films and magnetic multilayers. In particular, we
have analyzed the behavior of the critical edges for total external reflection
in both cases. For a single film we have observed experimentally and
theoretically a simple behavior: the critical edges remain fixed and the
intensity varies according to the angle between the polarization axis and the
magnetization vector inside the film. For the multilayer case we find that the
critical edges for spin up and spin down polarized neutrons move towards each
other as a function of the angle between the magnetization vectors in adjacent
ferromagnetic films. Although the results for multilayers and single thick
layers appear to be different, in fact the same spinor method explains both
results. An interpretation of the critical edges behavior for the multilyers as
a superposition of ferromagnetic and antifferomagnetic states is given.Comment: 6 pages, 5 figure
The Anomalous Hall effect in re-entrant AuFe alloys and the real space Berry phase
The Hall effect has been studied in a series of AuFe samples in the
re-entrant concentration range, as well as in the spin glass range. The data
demonstrate that the degree of canting of the local spins strongly modifies the
anomalous Hall effect, in agreement with theoretical predictions associating
canting, chirality and a real space Berry phase. The canonical parametrization
of the Hall signal for magnetic conductors becomes inappropriate when local
spins are canted.Comment: 4 pages, 1 eps figur
A Stellar Rotation Census of B Stars: from ZAMS to TAMS
Two recent observing campaigns provide us with moderate dispersion spectra of
more than 230 cluster and 370 field B stars. Combining them and the spectra of
the B stars from our previous investigations (430 cluster and 100
field B stars) yields a large, homogeneous sample for studying the rotational
properties of B stars. We derive the projected rotational velocity ,
effective temperature, gravity, mass, and critical rotation speed for each star. We find that the average is significantly lower
among field stars because they are systematically more evolved and spun down
than their cluster counterparts. The rotational distribution functions of
for the least evolved B stars show that lower mass B
stars are born with a larger proportion of rapid rotators than higher mass B
stars. However, the upper limit of that may separate
normal B stars from emission line Be stars (where rotation promotes mass loss
into a circumstellar disk) is smaller among the higher mass B stars. We compare
the evolutionary trends of rotation (measured according to the polar gravity of
the star) with recent models that treat internal mixing. The spin-down rates
observed in the high mass subset () agree with predictions, but
the rates are larger for the low mass group (). The faster spin
down in the low mass B stars matches well with the predictions based on
conservation of angular momentum in individual spherical shells. Our results
suggest the fastest rotators (that probably correspond to the emission line Be
stars) are probably formed by evolutionary spin up (for the more massive stars)
and by mass transfer in binaries (for the full range of B star masses).Comment: 44 pages, 10 figures, accepted for publication in Ap
Transition from van-der-Waals to H Bonds dominated Interaction in n-Propanol physisorbed on Graphite
Multilayer sorption isotherms of 1-propanol on graphite have been measured by
means of high-resolution ellipsometry within the liquid regime of the adsorbed
film for temperatures ranging from 180 to 260 K. In the first three monolayers
the molecules are oriented parallel to the substrate and the growth is roughly
consistent with the Frenkel-Halsey-Hill-model (FHH) that is obeyed in
van-der-Waals systems on strong substrates. The condensation of the fourth and
higher layers is delayed with respect to the FHH-model. The fourth layer is
actually a bilayer. Furthermore there is indication of a wetting transition.
The results are interpreted in terms of hydrogen-bridge bonding within and
between the layers.Comment: 4 pages, 3 figure
Monte Carlo studies of antiferromagnetic spin models in three dimensions
We study several antiferromagnetic formulations of the O(3) spin model in
three dimensions by means of Monte Carlo simulations. We discuss about the
vacua properties and analyze the phase transitions. Using Finite Size Scaling
analysis we conclude that all phase transitions found are of first orderComment: 4 pages, 2 Postscript figures. Contribution to Lattice '9
In-Network Outlier Detection in Wireless Sensor Networks
To address the problem of unsupervised outlier detection in wireless sensor
networks, we develop an approach that (1) is flexible with respect to the
outlier definition, (2) computes the result in-network to reduce both bandwidth
and energy usage,(3) only uses single hop communication thus permitting very
simple node failure detection and message reliability assurance mechanisms
(e.g., carrier-sense), and (4) seamlessly accommodates dynamic updates to data.
We examine performance using simulation with real sensor data streams. Our
results demonstrate that our approach is accurate and imposes a reasonable
communication load and level of power consumption.Comment: Extended version of a paper appearing in the Int'l Conference on
Distributed Computing Systems 200
Magnetoelectric effects in an organo-metallic quantum magnet
We observe a bilinear magnetic field-induced electric polarization of 50 in single crystals of NiCl-4SC(NH) (DTN). DTN forms a
tetragonal structure that breaks inversion symmetry, with the highly polar
thiourea molecules all tilted in the same direction along the c-axis.
Application of a magnetic field between 2 and 12 T induces canted
antiferromagnetism of the Ni spins and the resulting magnetization closely
tracks the electric polarization. We speculate that the Ni magnetic forces
acting on the soft organic lattice can create significant distortions and
modify the angles of the thiourea molecules, thereby creating a magnetoelectric
effect. This is an example of how magnetoelectric effects can be constructed in
organo-metallic single crystals by combining magnetic ions with electrically
polar organic elements.Comment: 3 pages, 3 figure
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