6,014 research outputs found
Minimizing the cost of fault location when testing from a finite state machine
If a test does not produce the expected output, the incorrect output may have been caused by an earlier state transfer failure. Ghedamsi and coworkers generate a set of candidates and then produce further tests to locate the failures within this set. We consider a special case where there is a state identification process that is known to be correct. A number of preset and adaptive approaches to fault location are described and the problem of minimizing the cost is explored. Some of the approaches lead to NP-hard optimization problems for which possible heuristics are suggested
Ultrafilters on -spaces
For a discrete group and a discrete -space , we identify the
Stone-\v{C}ech compactifications and with the sets of all
ultrafilters on and , and apply the natural action of on
to characterize large, thick, thin, sparse and scattered subsets of
. We use -invariant partitions and colorings to define -selective and
-Ramsey ultrafilters on . We show that, in contrast to the
set-theoretical case, these two classes of ultrafilters are distinct. We
consider also universally thin ultrafilters on , the -points, and
study interrelations between these ultrafilters and some classical ultrafilters
on
Generating Complete and Finite Test Suite for ioco: Is It Possible?
Testing from Input/Output Transition Systems has been intensely investigated.
The conformance between the implementation and the specification is often
determined by the so-called ioco-relation. However, generating tests for ioco
is usually hindered by the problem of conflicts between inputs and outputs.
Moreover, the generation is mainly based on nondeterministic methods, which may
deliver complete test suites but require an unbounded number of executions. In
this paper, we investigate whether it is possible to construct a finite test
suite which is complete in a predefined fault domain for the classical ioco
relation even in the presence of input/output conflicts. We demonstrate that it
is possible under certain assumptions about the specification and
implementation, by proposing a method for complete test generation, based on a
traditional method developed for FSM.Comment: In Proceedings MBT 2014, arXiv:1403.704
Classical Heisenberg antiferromagnet on a garnet lattice: a Monte Carlo simulation
We have studied a classical antiferromagnet on a garnet lattice by means of
Monte Carlo simulations in an attempt to examine the role of geometrical
frustration in Gadolinium Gallium Garnet, Gd3Ga5O12 (GGG). Low-temperature
specific heat, magnetisation, susceptibility, the autocorrelation function A(t)
and the neutron scattering function S(Q) have been calculated for several
models including different types of magnetic interactions and with the presence
of an external magnetic field applied along the principal symmetry axes. A
model, which includes only nearest-neighbour exchange, J1, neither orders down
to the lowest temperature nor does it show any tendency towards forming a
short-range coplanar spin structure. This model, however, does demonstrate a
magnetic field induced ordering below T ~ 0.01 J1. In order to reproduce the
experimentally observed properties of GGG, the simulated model must include
nearest neighbour exchange interactions and also dipolar forces. The presence
of weak next-to-nearest exchange interactions is found to be insignificant. In
zero field S(Q) exhibits diffuse magnetic scattering around positions in
reciprocal space where antiferromagnetic Bragg peaks appear in an applied
magnetic field.Comment: 8 pages, 8 figures, to appear in PRB (JAN 2001
Long-term evolution of broken wakefields in finite radius plasmas
A novel effect of fast heating and charging a finite-radius plasma is
discovered in the context of plasma wakefield acceleration. As the plasma wave
breaks, the most of its energy is transferred to plasma electrons which create
strong charge-separation electric field and azimuthal magnetic field around the
plasma. The slowly varying field structure is preserved for hundreds of
wakefield periods and contains (together with hot electrons) up to 80% of the
initial wakefield energy.Comment: 5 pages, 6 figure
Triangular Antiferromagnets
In this article we review the effects of magnetic frustation in the stacked
triangular lattice. Frustration increases the degeneracy of the ground state,
giving rise to different physics. In particular it leads to unique phase
diagrams with multicritical points and novel critical phenomena. We describe
the confrontation of theory and experiment for a number of systems with
differing magnetic Hamiltonians; Heisenberg, Heisenberg with easy-axis
anisotropy, Heisenberg with easy-plane anisotropy, Ising and singlet ground
state. Interestingly each leads to different magnetic properties and phase
diagrams. We also describe the effects of ferromagnetic, rather than
antiferromagnetic, stacking and of small distortions of the triangular lattice.Comment: Review article, 36 pages, revtex, 19 figures in PS format, to appear
in Can. J. Phy
- …