40,158 research outputs found
Analysis of edge impact stresses in composite plates
The in-plane edge impact of composite plates, with or without a protection strip, is investigated. A computational analysis based on the Fast Fourier Transform technique is presented. The particular application of the present method is in the understanding of the foreign object damage problem of composite fan blades. The method is completely general and may be applied to the study of other stress wave propagation problems in a half space. Results indicate that for the protective strip to be effective in reducing impact stresses in the composite the thickness must be equal or greater than the impact contact dimension. Large interface shear stresses at the strip - composite boundary can be induced under impact
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Modelling human behaviours and reactions under dangerous environment
This paper describes the framework of a real-time simulation system to model human behavior and reactions in dangerous environments. The system utilizes the latest 3D computer animation techniques, combined with artificial intelligence, robotics and psychology, to model human behavior, reactions and decision making under expected/unexpected dangers in real-time in virtual environments. The development of the system includes: classification on the conscious/subconscious behaviors and reactions of different people; capturing different motion postures by the Eagle Digital System; establishing 3D character animation models; establishing 3D models for the scene; planning the scenario and the contents; and programming within Virtools (TM) Dev. Programming within Virtools (TM) Dev is subdivided into modeling dangerous events, modeling character's perceptions, modeling character's decision making, modeling character's movements, modeling character's interaction with environment and setting up the virtual cameras. The real-time simulation of human reactions in hazardous environments is invaluable in military defense, fire escape, rescue operation planning, traffic safety studies, and safety planning in chemical factories, the design of buildings, airplanes, ships and trains. Currently, human motion modeling can be realized through established technology, whereas to integrate perception and intelligence into virtual human's motion is still a huge undertaking. The challenges here are the synchronization of motion and intelligence, the accurate modeling of human's vision, smell, touch and hearing, the diversity and effects of emotion and personality in decision making. There are three types of software platforms which could be employed to realize the motion and intelligence within one system, and their advantages and disadvantages are discussed
Neutrino Oscillations and Lepton Flavor Mixing
In view of the recent announcement on non-zero neutrino mass from
Super-Kamiokande experiment, it would be very timely to investigate all the
possible scenarios on masses and mixings of light neutrinos. Recently suggested
mass matrix texture for the quark CKM mixing, which can be originated from the
family permutation symmetry and its suitable breakings, is assumed for the
neutrino mass matrix and determined by the four combinations of solar,
atmospheric and LSND neutrino data and cosmological hot dark matter bound as
input constraints. The charged-lepton mass matrix is assumed to be diagonal so
that the neutrino mixing matrix can be identified directly as the lepton flavor
mixing matrix and no CP invariance violation originates from the leptonic
sector. The results favor hierarchical patterns for the neutrino masses, which
follow from the case when either solar-atmospheric data or solar-HDM
constraints are used.Comment: Latex, 9 page
A Typology of Knowledge Co-creation in Social Networks
Creating new knowledge is a core process in managing and enabling knowledge especially though socialisation in social networks. The social nature of social technologies and knowledge creation attracts research on knowledge creation in social networks. Social technologies a less costly but yet collaborative and diverse platforms for social networking, creating new knowledge and leveraging personal and collective knowledge. Building a knowing organisation may extend beyond knowledge sharing into creation of new knowledge. This paper explores existing aspects regarding joint creation of knowledge “knowledge co-creation” in social networks. The paper demonstrates how the empirical ideas on co-creation can be useful in exploring knowledge co-creation. This discussion explores and introduces the scope of knowledge co-creation in online social networks. We derive a typology of knowledge co-creation that suggests pathways and hypothetical propositions into exploring knowledge co-creation of in social networks
Electronic structure of YbB: Is it a Topological Insulator or not?
To resolve the controversial issue of the topological nature of the
electronic structure of YbB, we have made a combined study using density
functional theory (DFT) and angle resolved photoemission spectroscopy (ARPES).
Accurate determination of the low energy band topology in DFT requires the use
of modified Becke-Johnson exchange potential incorporating the spin-orbit
coupling and the on-site Coulomb interaction of Yb electrons as large
as 7 eV. We have double-checked the DFT result with the more precise GW band
calculation. ARPES is done with the non-polar (110) surface termination to
avoid band bending and quantum well confinement that have confused ARPES
spectra taken on the polar (001) surface termination. Thereby we show
definitively that YbB has a topologically trivial B 2-Yb 5
semiconductor band gap, and hence is a non-Kondo non-topological insulator
(TI). In agreement with theory, ARPES shows pure divalency for Yb and a -
band gap of 0.3 eV, which clearly rules out both of the previous scenarios of
- band inversion Kondo TI and - band inversion non-Kondo TI. We
have also examined the pressure-dependent electronic structure of YbB,
and found that the high pressure phase is not a Kondo TI but a
\emph{p}-\emph{d} overlap semimetal.Comment: The main text is 6 pages with 4 figures, and the supplementary
information contains 6 figures. 11 pages, 10 figures in total To be appeared
in Phys. Rev. Lett. (Online publication is around March 16 if no delays.
Phonon emission and absorption in the fractional quantum Hall effect
We investigate the time dependent thermal relaxation of a two-dimensional
electron system in the fractional quantum Hall regime where ballistic phonons
are used to heat up the system to a non-equilibrium temperature. The thermal
relaxation of a 2DES at can be described in terms of a broad band
emission of phonons, with a temperature dependence proportional to . In
contrast, the relaxation at fractional filling is characterized by
phonon emission around a single energy, the magneto-roton gap. This leads to a
strongly reduced energy relaxation rate compared to with only a weak
temperature dependence for temperatures 150 mK 400 mK.Comment: 4 pages, 3 figures; 14th International Conference on High Magnetic
Fields in Semiconductor Physics, September 24-29, 2000, Matsue, Japa
Spatial Organization in the Reaction A + B --> inert for Particles with a Drift
We describe the spatial structure of particles in the (one dimensional)
two-species annihilation reaction A + B --> 0, where both species have a
uniform drift in the same direction and like species have a hard core
exclusion. For the case of equal initial concentration, at long times, there
are three relevant length scales: the typical distance between similar
(neighboring) particles, the typical distance between dissimilar (neighboring)
particles, and the typical size of a cluster of one type of particles. These
length scales are found to be generically different than that found for
particles without a drift.Comment: 10 pp of gzipped uuencoded postscrip
Magnetic field splitting of the spin-resonance in CeCoIn5
Neutron scattering in strong magnetic fields is used to show the
spin-resonance in superconducting CeCoIn5 (Tc=2.3 K) is a doublet. The
underdamped resonance (\hbar \Gamma=0.069 \pm 0.019 meV) Zeeman splits into two
modes at E_{\pm}=\hbar \Omega_{0}\pm g\mu_{B} \mu_{0}H with g=0.96 \pm 0.05. A
linear extrapolation of the lower peak reaches zero energy at 11.2 \pm 0.5 T,
near the critical field for the incommensurate "Q-phase" indicating that the
Q-phase is a bose condensate of spin excitons.Comment: 5 pages, 4 figure
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