32,726 research outputs found
Dependency Schemes in QBF Calculi: Semantics and Soundness
We study the parametrisation of QBF resolution calculi by dependency schemes. One of the main problems in this area is to understand for which dependency schemes the resulting calculi are sound. Towards this end we propose a semantic framework for variable independence based on ‘exhibition’ by QBF models, and use it to express a property of dependency schemes called full exhibition that is known to be sufficient for soundness in Q-resolution. Introducing a generalised form of the long-distance resolution rule, we propose a complete parametrisation of classical long-distance Q-resolution, and show that full exhibition remains sufficient for soundness. We demonstrate that our approach applies to the current research frontiers by proving that the reflexive resolution path dependency scheme is fully exhibited
Background reduction and sensitivity for germanium double beta decay experiments
Germanium detectors have very good capabilities for the investigation of rare
phenomena like the neutrinoless double beta decay. Rejection of the background
entangling the expected signal is one primary goal in this kind of experiments.
Here, the attainable background reduction in the energy region where the
neutrinoless double beta decay signal of 76Ge is expected to appear has been
evaluated for experiments using germanium detectors, taking into consideration
different strategies like the granularity of the detector system, the
segmentation of each individual germanium detector and the application of Pulse
Shape Analysis techniques to discriminate signal from background events.
Detection efficiency to the signal is affected by background rejection
techniques, and therefore it has been estimated for each of the background
rejection scenarios considered. Finally, conditions regarding crystal mass,
radiopurity, exposure to cosmic rays, shielding and rejection capabilities are
discussed with the aim to achieve a background level of 10-3 c keV-1 kg-1 y-1
in the region of interest, which would allow to explore neutrino effective
masses around 40 meV.Comment: 13 pages, 19 figures. Accepted by Astroparticle Physic
Key Generation in Wireless Sensor Networks Based on Frequency-selective Channels - Design, Implementation, and Analysis
Key management in wireless sensor networks faces several new challenges. The
scale, resource limitations, and new threats such as node capture necessitate
the use of an on-line key generation by the nodes themselves. However, the cost
of such schemes is high since their secrecy is based on computational
complexity. Recently, several research contributions justified that the
wireless channel itself can be used to generate information-theoretic secure
keys. By exchanging sampling messages during movement, a bit string can be
derived that is only known to the involved entities. Yet, movement is not the
only possibility to generate randomness. The channel response is also strongly
dependent on the frequency of the transmitted signal. In our work, we introduce
a protocol for key generation based on the frequency-selectivity of channel
fading. The practical advantage of this approach is that we do not require node
movement. Thus, the frequent case of a sensor network with static motes is
supported. Furthermore, the error correction property of the protocol mitigates
the effects of measurement errors and other temporal effects, giving rise to an
agreement rate of over 97%. We show the applicability of our protocol by
implementing it on MICAz motes, and evaluate its robustness and secrecy through
experiments and analysis.Comment: Submitted to IEEE Transactions on Dependable and Secure Computin
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