303 research outputs found
Using domain-independent problems for introducing formal methods
The key to the integration of formal methods into engineering practice is education. In teaching, domain-independent problems i.e., not requiring prior engineering background-offer many advantages.
Such problems are widely available, but this paper adds two dimensions that are lacking in typical solutions yet are crucial to formal methods: (i) the translation of informal statements into formal expressions; (ii) the role of formal calculation (including proofs) in exposing risks or misunderstandings and in discovering pathways to solutions.
A few example problems illustrate this: (a) a small logical one showing the importance of fully capturing informal statements; (b) a combinatorial one showing how, in going from "real-world" formulations to mathematical ones, formal methods can cover more aspects than classical mathematics, and a half-page formal program semantics suitable for beginners is presented as a support; (c) a larger one showing how a single problem can contain enough elements to serve as a Leitmotiv for all notational and reasoning issues in a complete introductory course.
An important final observation is that, in teaching formal methods, no approach can be a substitute for an open mind, as extreme mathphobia appears resistant to any motivation
Homogeneity of Stellar Populations in Early-Type Galaxies with Different X-ray Properties
We have found the stellar populations of early-type galaxies are homogeneous
with no significant difference in color or Mg2 index, despite the dichotomy
between X-ray extended early-type galaxies and X-ray compact ones. Since the
X-ray properties reflect the potential gravitational structure and hence the
process of galaxy formation, the homogeneity of the stellar populations implies
that the formation of stars in early-type galaxies predat es the epoch when the
dichotomy of the potential structure was established.Comment: 6 pages, 5 figures, accepted for publication in Ap
Coalition theories: empirical evidence for dutch municipalities
The paper analyzes coalition formation in Dutch municipalities. After discussing the main features of the institutional setting, several theories are discussed, which are classified as size oriented, policy oriented and actor oriented models. A test statistic is proposed to determine the predictive power of these models. The empirical analysis shows that strategic positions as well as some of the distinguished preferences are important in the setting of Dutch municipalities. Especially, the dominant minimum number principle yields highly significant results for coalition formations in the period 1978–1986
Which mathematics for the Information Society?
MathIS is a new project that aims to reinvigorate secondary- school mathematics by exploiting insights of the dynamics of algorithmic problem solving. This paper describes the main ideas that underpin the project. In summary, we propose a central role for formal logic, the development of a calculational style of reasoning, the emphasis on the algorithmic nature of mathematics, and the promotion of self-discovery by the students. These ideas are discussed and the case is made, through a number of examples that show the teaching style that we want to introduce, for their relevance in shaping mathematics training for the years to come. In our opinion, the education of software engineers that work effectively with formal methods and mathematical abstractions should start before university and would benefit from the ideas discussed here.Long-term collaboration with J. N. Oliveira on calculational approaches to mathematics is deeply acknowledged. We are also grateful to the anonymous referees for their valuable comments. This research was supported by FCT (the Portuguese Foundation for Science and Technology), in the context of the MATHIS Project under contract PTDC/EIA/73252/2006. The work of Joao F. Ferreira and AlexandraMendeswas further supported by FCT grants SFRH/BD/24269/2005 and SFRH/BD/29553/2006, respectively
Distinguishing sequences for partially specified FSMs
Distinguishing Sequences (DSs) are used inmany Finite State Machine (FSM) based test techniques. Although Partially Specified FSMs (PSFSMs) generalise FSMs, the computational complexity of constructing Adaptive and Preset DSs (ADSs/PDSs) for PSFSMs has not been addressed. This paper shows that it is possible to check the existence of an ADS in polynomial time but the corresponding problem for PDSs is PSPACE-complete. We also report on the results of experiments with benchmarks and over 8 * 106 PSFSMs. © 2014 Springer International Publishing
Active-Sterile neutrino oscillations and BBN+CMBR constraints
We show how active-sterile neutrino oscillations in the early Universe can
play an interesting role in explaining the current observations of CMBR
anisotropies and light element abundances. We describe different possible
phenomenological scenarios in the interpretation of present data and how
active-sterile neutrino oscillations can provide a viable theoretical
framework.Comment: Some changes, to appear in Phys. Rev.
Anatomy of a Merger: A Numerical Model of A754
A754 is a well-observed cluster of galaxies which exhibits a variety of
morphological peculiarities. These include a bar of X-ray emission that is
offset significantly from the galaxy distribution, an elongated X-ray surface
brightness distribution extending between two distinct peaks in the galaxy
distribution, and an extremely non-isothermal and asymmetric intracluster
medium (ICM) temperature morphology. Using these observational constraints, we
present a numerical Hydro/N-body model of A754 in which two clusters (2.5:1
mass ratio) have merged nearly in the plane of the sky less than 0.5 Gyrs ago
with an impact parameter of ~120 kpc, and an impact velocity of ~2500 km/s
(roughly the escape velocity of the primary cluster). Our models allow us to
identify the origin of A754's peculiar X-ray and temperature morphologies, the
underlying hydrodynamical processes that shape them, and their future
evolution. We make detailed predictions for future high resolution X-ray
spectroscopic observations (e.g. ASTRO-E). We discuss general properties of our
models which will be characteristic of off-axis mergers. In particular, we find
significant non-thermal pressure support within the central region which could
bias cluster mass estimates. We find significant angular momentum imparted on
the gas distribution in the cluster. We find that mixing of the subcluster gas
components is an inefficient process, particularly at large radii. Finally, we
find that subsequent dark matter core passages result in an extended relaxation
timescale.Comment: 27 pages, including tables and figures. Latex, 10 postscript figures.
Figures 2, 6, and 7 are color, but will also print as B/W. Accepted for
publication in the Astrophysical Journa
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