54,917 research outputs found
A Study of the PDGF Signaling Pathway with PRISM
In this paper, we apply the probabilistic model checker PRISM to the analysis
of a biological system -- the Platelet-Derived Growth Factor (PDGF) signaling
pathway, demonstrating in detail how this pathway can be analyzed in PRISM. We
show that quantitative verification can yield a better understanding of the
PDGF signaling pathway.Comment: In Proceedings CompMod 2011, arXiv:1109.104
Probabilistically safe vehicle control in a hostile environment
In this paper we present an approach to control a vehicle in a hostile environment with static obstacles and moving adversaries. The vehicle is required to satisfy a mission objective expressed as a temporal logic specification over a set of properties satisfied at regions of a partitioned environment. We model the movements of adversaries in between regions of the environment as Poisson processes. Furthermore, we assume that the time it takes for the vehicle to traverse in between two facets of each region is exponentially distributed, and we obtain the rate of this exponential distribution from a simulator of the environment. We capture the motion of the vehicle and the vehicle updates of adversaries distributions as a Markov Decision Process. Using tools in Probabilistic Computational Tree Logic, we find a control strategy for the vehicle that maximizes the probability of accomplishing the mission objective. We demonstrate our approach with illustrative case studies
LTL Control in Uncertain Environments with Probabilistic Satisfaction Guarantees
We present a method to generate a robot control strategy that maximizes the
probability to accomplish a task. The task is given as a Linear Temporal Logic
(LTL) formula over a set of properties that can be satisfied at the regions of
a partitioned environment. We assume that the probabilities with which the
properties are satisfied at the regions are known, and the robot can determine
the truth value of a proposition only at the current region. Motivated by
several results on partitioned-based abstractions, we assume that the motion is
performed on a graph. To account for noisy sensors and actuators, we assume
that a control action enables several transitions with known probabilities. We
show that this problem can be reduced to the problem of generating a control
policy for a Markov Decision Process (MDP) such that the probability of
satisfying an LTL formula over its states is maximized. We provide a complete
solution for the latter problem that builds on existing results from
probabilistic model checking. We include an illustrative case study.Comment: Technical Report accompanying IFAC 201
A counter abstraction technique for the verification of robot swarms.
We study parameterised verification of robot swarms against temporal-epistemic specifications. We relax some of the significant restrictions assumed in the literature and present a counter abstraction approach that enable us to verify a potentially much smaller abstract model when checking a formula on a swarm of any size. We present an implementation and discuss experimental results obtained for the alpha algorithm for robot swarms
Interaction between a fast rotating sunspot and ephemeral regions as the origin of the major solar event on 2006 December 13
The major solar event on 2006 December 13 is characterized by the
approximately simultaneous occurrence of a heap of hot ejecta, a great
two-ribbon flare and an extended Earth-directed coronal mass ejection. We
examine the magnetic field and sunspot evolution in active region NOAA AR
10930, the source region of the event, while it transited the solar disk centre
from Dec. 10 to Dec. 13. We find that the obvious changes in the active region
associated with the event are the development of magnetic shear, the appearance
of ephemeral regions and fast rotation of a smaller sunspot. Around the area of
the magnetic neutral line of the active region, interaction between the fast
rotating sunspot and the ephemeral regions triggers continual brightening and
finally the major flare. It is indicative that only after the sunspot rotates
up to 200 does the major event take place. The sunspot rotates at
least 240 about its centre, the largest sunspot rotation angle which
has been reported.Comment: 4 pages, 6 figures, ApJ Letters inpres
First Evidence of Coexisting EIT Wave and Coronal Moreton Wave from SDO/AIA Observations
"EIT waves" are a globally propagating wavelike phenomenon. They were often
interpreted as a fast-mode magnetoacoustic wave in the corona, despite various
discrepancies between the fast-mode wave model and observations. To reconcile
these discrepancies, we once proposed that "EIT waves" are apparent propagation
of the plasma compression due to successive stretching of the magnetic field
lines pushed by the erupting flux rope. According to this model, an "EIT wave"
should be preceded by a fast-mode wave, which however was rarely observed. With
the unprecedented high cadence and sensitivity of the {\em Solar Dynamics
Observatory} ({\em SDO}) observations, we discern a fast-moving wave front with
a speed of 560 km s, ahead of an "EIT wave", which had a velocity of
km s, in the "EIT wave" event on 2010 July 27. The results,
suggesting that "EIT waves" are not fast-mode waves, confirm the prediction of
our fieldline stretching model for "EIT wave". In particular, it is found that
the coronal Moreton wave was times faster than the "EIT wave" as
predicted.Comment: 13 pages, 4 figures, submitted for publication in ApJ Letter
Factorizing -matrices and the XXZ spin-1/2 chain: A diagrammatic perspective
Using notation inherited from the six-vertex model, we construct diagrams
that represent the action of the factorizing -matrices associated to the
finite length XXZ spin-1/2 chain. We prove that these -matrices factorize
the tensor corresponding with elements of the permutation
group. We consider in particular the diagram for the tensor , which cyclically permutes the spin chain. This leads us to a diagrammatic
construction of the local spin operators and in terms of
the monodromy matrix operators.Comment: 26 pages, extra references added, typographical errors correcte
- …