22,129 research outputs found
A Supervisory Control Algorithm Based on Property-Directed Reachability
We present an algorithm for synthesising a controller (supervisor) for a
discrete event system (DES) based on the property-directed reachability (PDR)
model checking algorithm. The discrete event systems framework is useful in
both software, automation and manufacturing, as problems from those domains can
be modelled as discrete supervisory control problems. As a formal framework,
DES is also similar to domains for which the field of formal methods for
computer science has developed techniques and tools. In this paper, we attempt
to marry the two by adapting PDR to the problem of controller synthesis. The
resulting algorithm takes as input a transition system with forbidden states
and uncontrollable transitions, and synthesises a safe and
minimally-restrictive controller, correct-by-design. We also present an
implementation along with experimental results, showing that the algorithm has
potential as a part of the solution to the greater effort of formal supervisory
controller synthesis and verification.Comment: 16 pages; presented at Haifa Verification Conference 2017, the final
publication is available at Springer via
https://doi.org/10.1007/978-3-319-70389-3_
Algorithmic Verification of Continuous and Hybrid Systems
We provide a tutorial introduction to reachability computation, a class of
computational techniques that exports verification technology toward continuous
and hybrid systems. For open under-determined systems, this technique can
sometimes replace an infinite number of simulations.Comment: In Proceedings INFINITY 2013, arXiv:1402.661
Electromagnetic Waves in Variable Media
Two methods are explained to exactly solve Maxwell's equations where
permittivity, permeability and conductivity may vary in space. In the
constitutive relations, retardation is regarded. If the material properties
depend but on one coordinate, general solutions are derived. If the properties
depend on two coordinates, geometrically restricted solutions are obtained.
Applications to graded reflectors, especially to dielectric mirrors, to
filters, polarizers and to waveguides, plain and cylindrical, are indicated.
New foundations for the design of optical instruments, which are centered
around an axis, and for the design of invisibility cloaks, plain and spherical,
are proposed. The variability of material properties makes possible effects
which cannot happen in constant media, e.g. stopping the flux of
electromagnetic energy without loss. As a consequence, spherical devices can be
constructed which bind electromagnetic waves
Potential of the J-PET detector for studies of discrete symmetries in decays of positronium atom - a purely leptonic system
The Jagiellonian Positron Emission Tomograph (J-PET) was constructed as a
prototype of the cost-effective scanner for the simultaneous metabolic imaging
of the whole human body. Being optimized for the detection of photons from the
electron-positron annihilation with high time- and high angular-resolution, it
constitutes a multi-purpose detector providing new opportunities for studying
the decays of positronium atoms. Positronium is the lightest purely leptonic
object decaying into photons. As an atom bound by a central potential it is a
parity eigenstate, and as an atom built out of an electron and an anti-electron
it is an eigenstate of the charge conjugation operator. Therefore, the
positronium is a unique laboratory to study discrete symmetries whose precision
is limited in principle by the effects due to the weak interactions expected at
the level of (~10) and photon-photon interactions expected at the level
of (~10). The J-PET detector enables to perform tests of discrete
symmetries in the leptonic sector via the determination of the expectation
values of the discrete-symmetries-odd operators, which may be constructed from
the spin of ortho-positronium atom and the momenta and polarization vectors of
photons originating from its annihilation. In this article we present the
potential of the J-PET detector to test the C, CP, T and CPT symmetries in the
decays of positronium atoms.Comment: 27 pages, 6 figure
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