978 research outputs found
Polarization measurements and their perspectives: PVLAS Phase II
We sketch the proposal for a "PVLAS-Phase II" experiment. The main physics
goal is to achieve the first direct observation of non-linear effects in
electromagnetism predicted by QED and the measurement of the photon-photon
scattering cross section at low energies (1-2 eV). Physical processes such as
ALP and MCP production in a magnetic field could also be accessible if
sensitive enough operation is reached. The short term experimental strategy is
to compact as much as possible the dimensions of the apparatus in order to
bring noise sources under control and to attain a sufficient sensitivity. We
will also briefly mention future pespectives, such as a scheme to implement the
resonant regeneration principle for the detection of ALPs.Comment: Paper submitted to the proceedings of the "4th Patras Workshop on
Axions, WIMPs and WISPs", DESY, Hamburg Site /Germany, 18-21 June 200
SAN models of communication scenarios inside the Electrical Power System
This report provides all the details about the models and the quantitative results presented in [1], about the simulation of communication scenarios inside the Electrical Power System. In particular, the scenarios deal with the communication between one area control centre and a set of substations in a distribution grid, exchanging commands and signals by means of a redundant communication network. The communication may be affected by threats such as the communication network failure, or intrusions into the communication, causing the loss of commands or signals. The scenarios have been modeled and simulated in form of Stochastic Activity Networks, with the purpose of evaluating the effects of such threats on the communication reliability
Alternative Buffer-Layers for the Growth of SrBi2Ta2O9 on Silicon
In this work we investigate the influence of the use of YSZ and CeO2/YSZ as
insulators for Metal- Ferroelectric-Insulator-Semiconductor (MFIS) structures
made with SrBi2Ta2O9 (SBT). We show that by using YSZ only the a-axis oriented
Pyrochlore phase could be obtained. On the other hand the use of a CeO2/YSZ
double-buffer layer gave a c-axis oriented SBT with no amorphous SiO2 inter-
diffusion layer. The characteristics of MFIS diodes were greatly improved by
the use of the double buffer. Using the same deposition conditions the memory
window could be increased from 0.3 V to 0.9 V. From the piezoelectric response,
nano-meter scale ferroelectric domains could be clearly identified in SBT thin
films.Comment: 5 pages, 9 figures, 13 refernece
Color Variability of the Blazar AO 0235+16
Multicolor (UBVRIJHK) observations of the blazar AO 0235+16 are analyzed. The
light curves were compiled at the Turin Observatory from literature data and
the results of observations obtained in the framework of the WEBT program
(http://www.to.astro/blazars/webt/). The color variability of the blazar was
studied in eight time intervals with a sufficient number of multicolor optical
observations; JHK data are available for only one of these. The spectral energy
distribution (SED) of the variable component remained constant within each
interval, but varied strongly from one interval to another. After correction
for dust absorption, the SED can be represented by a power law in all cases,
providing evidence for a synchrotron nature of the variable component. We show
that the variability at both optical and IR wavelengths is associated with the
same variable source.Comment: 11 pages, 9 figures, 4 tables, accepted for publication in Astronomy
Report
Decision Networks for modeling and analysis of attack/defense scenarios in critical infrastructures
We propose to exploit Decision Networks (DN) for the analysis of attack/defense scenarios. We show that DN extend both the modeling and the analysis capabilities of formalisms based on Attack Trees, which are the main reference model in such a context. Uncertainty can be addressed at every system level and a decision-theoretic analysis of the risk and of the selection of the best countermeasures can be implemented, by exploiting standard inference algorithms on DN
A new structural model for disorder in vaterite from first-principles calculations
Both of the previously proposed Pbnm and P6522 ordered structures for vaterite are found to be unstable transition states using first principles methods. Five stable structures are located, the lowest energy one being of P3221 symmetry. Since interconversion between these structures requires only thermal energy, this provides an additional source of disorder within the vaterite structure
Influence of Temperature and Anisotropic Pressure on the Phase Transitions in α-Cristobalite
The role of temperature and anisotropy of the applied load in the pressure–induced transformations of α -cristobalite is investigated by means of first principles molecular dynamics combined with the metadynamics algorithm for the study of solid-solid phase transitions. We reproduce the transition to α-PbO2 as found in experiments and we observe that the transition paths are qualitatively different and yield different products when a nonhydrostatic load is applied, giving rise to a new class of metastable structures with mixed tetrahedral and octahedral coordination
Remarks on Conserved Quantities and Entropy of BTZ Black Hole Solutions. Part II: BCEA Theory
The BTZ black hole solution for (2+1)-spacetime is considered as a solution
of a triad-affine theory (BCEA) in which topological matter is introduced to
replace the cosmological constant in the model. Conserved quantities and
entropy are calculated via Noether theorem, reproducing in a geometrical and
global framework earlier results found in the literature using local
formalisms. Ambiguities in global definitions of conserved quantities are
considered in detail. A dual and covariant Legendre transformation is performed
to re-formulate BCEA theory as a purely metric (natural) theory (BCG) coupled
to topological matter. No ambiguities in the definition of mass and angular
momentum arise in BCG theory. Moreover, gravitational and matter contributions
to conserved quantities and entropy are isolated. Finally, a comparison of BCEA
and BCG theories is carried out by relying on the results obtained in both
theories.Comment: PlainTEX, 20 page
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