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

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

Working Group on Electrical Trawling (WGELECTRA; outputs from 2021)

The Working Group on Electrical Trawling creates a platform for supra-national joint research projects on electro-trawling and scientific publications. The group also reviews all relevant studies on marine electrofishing and discusses the ongoing and upcoming research projects in the light of knowledge gaps. Research areas covered by the group included fishing tactics and dynamics, organisms and ecological impacts and selectivity of electro trawling. A study into the exploitation of local fishing grounds revealed that pulse trawlers and conventional tickler chain beam trawlers had similar tactics spending 10% of their tows searching for a fishing ground and spending 90% of their tows exploiting a fishing ground. In-situ field campaigns revealed a lower impact of pulse trawls on biogeochemical parameters compared to traditional beam trawl methods. Laboratory experiments found that while alternating or pulsed bipolar currents readily penetrated the sediment, biogeochemical effects appeared to be inhibited from occurring. The combined results concluded that the environmental impact of electricity from pulse trawls is relatively minor compared to the mechanical disturbances created from the same gears. Behavioral response thresholds for pulsed electric fields were determined in laboratory experiments for electroreceptive as well as non-electroreceptive fish species. Comparison of these thresholds to simulations of electric fields around commercial fishing gears suggest that electrical pulses are unlikely to substantially affect the investigated fish species outside the trawl track. A field study into direct mortality among fish and benthic organisms in the wake of pulse trawlers refuted claims that pulse trawling causes mass mortality among non-target species. A study into the selectivity of shrimp pulse trawling vs. traditional trawling concluded that that shrimp fishing using pulse gear does not result in higher amounts of undesired bycatches of small shrimp, fish and benthos when compared to the traditional shrimp beam trawl fisheries. The outline of a PhD project that started in 2021 into organism and ecological impacts of electrofishing for razor clams in Scottish shallow coastal habitats was presented and preliminary results were shared

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

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