9,518 research outputs found
Interactive Simplifier Tracing and Debugging in Isabelle
The Isabelle proof assistant comes equipped with a very powerful tactic for
term simplification. While tremendously useful, the results of simplifying a
term do not always match the user's expectation: sometimes, the resulting term
is not in the form the user expected, or the simplifier fails to apply a rule.
We describe a new, interactive tracing facility which offers insight into the
hierarchical structure of the simplification with user-defined filtering,
memoization and search. The new simplifier trace is integrated into the
Isabelle/jEdit Prover IDE.Comment: Conferences on Intelligent Computer Mathematics, 201
Thyroid growth stimulating activity in higly purified lgG-fractions of patients with nonimmune thyroid diseases
Isabelle/PIDE as Platform for Educational Tools
The Isabelle/PIDE platform addresses the question whether proof assistants of
the LCF family are suitable as technological basis for educational tools. The
traditionally strong logical foundations of systems like HOL, Coq, or Isabelle
have so far been counter-balanced by somewhat inaccessible interaction via the
TTY (or minor variations like the well-known Proof General / Emacs interface).
Thus the fundamental question of math education tools with fully-formal
background theories has often been answered negatively due to accidental
weaknesses of existing proof engines.
The idea of "PIDE" (which means "Prover IDE") is to integrate existing
provers like Isabelle into a larger environment, that facilitates access by
end-users and other tools. We use Scala to expose the proof engine in ML to the
JVM world, where many user-interfaces, editor frameworks, and educational tools
already exist. This shall ultimately lead to combined mathematical assistants,
where the logical engine is in the background, without obstructing the view on
applications of formal methods, formalized mathematics, and math education in
particular.Comment: In Proceedings THedu'11, arXiv:1202.453
Capturing Hiproofs in HOL Light
Hierarchical proof trees (hiproofs for short) add structure to ordinary proof
trees, by allowing portions of trees to be hierarchically nested. The
additional structure can be used to abstract away from details, or to label
particular portions to explain their purpose. In this paper we present two
complementary methods for capturing hiproofs in HOL Light, along with a tool to
produce web-based visualisations. The first method uses tactic recording, by
modifying tactics to record their arguments and construct a hierarchical tree;
this allows a tactic proof script to be modified. The second method uses proof
recording, which extends the HOL Light kernel to record hierachical proof trees
alongside theorems. This method is less invasive, but requires care to manage
the size of the recorded objects. We have implemented both methods, resulting
in two systems: Tactician and HipCam
Numerical investigation of the stability of stationary solutions in the theory of cathode spots in arcs in vacuum and ambient gas
The stability of stationary spots on cathodes of arcs in vacuum and ambient gas is investigated
by means of the simulation of the temporal evolution of perturbations imposed over
steady-state solutions. Two cases of loading conditions are considered, namely, spots
operating at a fixed current (the case typical of small-scale experiments) and spots operating at
a fixed voltage (the case typical of high-power circuit breakers). Results are reported on spots
on large copper cathodes of vacuum arcs and on spots on tungsten cathodes of high-pressure
argon arcs. It is shown, in particular, that if the ballast resistance in small-scale laboratory
experiments with a high-current arc is insufficient, the potential consequence may be a thermal
explosion of a spot, if the arc burns in vacuum, and massive melting of the cathode surface, if
the arc burns in ambient gas. This conclusion conforms to trends observed in the experiment.info:eu-repo/semantics/publishedVersio
Pronounced genetic structure and low genetic diversity in European red-billed chough (Pyrrhocorax pyrrhocorax) populations
Conservation Genetics August 2015, Volume 16, Issue 4, pp 1011–1012 Erratum to: Pronounced genetic structure and low genetic diversity in European red-billed chough (Pyrrhocorax pyrrhocorax) populations Erratum to: Conserv Genet (2012) 13:1213–1230 DOI 10.1007/s10592-012-0366-6 In the original publication, Tables 3 and 6 were published with incorrect estimates of population heterozygosities. All other diversity statistics were correct as originally presented. Updated versions of Tables 3 and 6 with corrected heterozygosity estimates confirmed using Arlequin 3.5 (Excoffier and Lischer 2010) as in Dávila et al. (2014) are provided in this erratum. Discrepancies were minor for populations on the British Isles. The correct estimates for Spain are slightly larger than those reported for La Palma by Dávila et al. (2014), but this does not necessarily affect their interpretation that choughs on La Palma may have originated from multiple migration events. The original conclusion that chough populations on the British Isles have low genetic diversity compared to continental European populations remains and is now, in fact, strengthened.Peer reviewedPostprin
Simulation of thermal instability in non-uniformities on the surface of cathodes of vacuum arcs
Instability stemming from the strong dependence
of electron emission current on the local surface
temperature plays an important role in current transfer to
hot cathodes of arc discharges. In the case of vacuum arcs,
this instability may lead to micro explosions on cathode
surface even if the surface is planar. This work is
concerned with numerical simulation of effect produced by
surface non-uniformities. It is found that the effect is
non-trivial: the presence of surface non-uniformities can
not only accelerate the development of the instability,
which is what one would expect intuitively, but also slow it
down and even suppress.info:eu-repo/semantics/publishedVersio
Phenomenological approach to simulation of propagation of spots over cathodes of high-power vacuum circuit breakers
A phenomenological description of an ensemble
of a large number of spots on negative contacts of
high-power vacuum circuit breakers is developed by
means of generalization of the concept of random walk of a
single cathode spot in low-current vacuum arcs. The model
is formulated in terms of a convection-diffusion equation
governing the evolution of the number of spots per unit
area, taking into account the variation of the number of
spots with the arc current and the “retrograde repulsion”
between spots. The approach is applied to description of
the distribution of cathode spots during the initial
expansion process after arc ignition in conditions of two
independent experiments simulating high-power switches.
A reasonably good agreement between the theory and the
experiment is found. The developed model can be used as a
module of global numerical models of the interruption
process in high-power vacuum circuit breakers.info:eu-repo/semantics/publishedVersio
Monte Carlo study of the critical properties of the three-dimensional 120-degree model
We report on large scale finite-temperature Monte Carlo simulations of the
classical or orbital-only model on the simple cubic lattice
in three dimensions with a focus towards its critical properties. This model
displays a continuous phase transition to an orbitally ordered phase. While the
correlation length exponent is close to the 3D XY value, the
exponent differs substantially from O(N) values. We also
introduce a discrete variant of the model, called -clock model,
which is found to display the same set of exponents. Further, an emergent U(1)
symmetry is found at the critical point , which persists for below
a crossover length scaling as , with an unusually small
.Comment: 13 pages, 6 figure
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