Top-down design in the context of parallel programs

A class of parallel programs, based on Free Choice Petri nets, is modeled by associating operators and predicates with vertices of the net. The model, called a formal parallel program (FPP), forms a natural extension of flow-chart notation to parallel programs. Definitions are made of the behaviour of an FPP, and the simulation of one FPP by another. A class of top-down FPPs is next defined, by requiring program graphs to be obtained through successive refinement steps, using a restricted set of control structures. Using the above definitions, it is shown that there exists an FPP ℰ satisfying the property that for any top-down FPP ℰ′ simulating ℰ, the degree of parallelism attainable in ℰ′ is smaller than that in ℰ. The measure of parallelism used is the number of different ways of carrying out a computation. In the case of parallel programs, this phenomenon of loss of parallelism therefore uncovers a performance factor which may offset some of the advantages of using top-down design

On the interconnection structure of cellular networks

This paper presents a model which can be used to represent many of the interconnection patterns commonly found in cellular networks. This model is then used to classify cellular networks according to the degree of regularity in their interconnection patterns. Specifically, three classes of cellular networks, corresponding to three forms of interconnection regularity, are defined. A concept of network realization is then developed to detect structural similarities in different networks and is used to compare the computational capabilities of these three classes

Seismic history from in situ 36Cl cosmogenic nuclide data on limestone fault scarps using Bayesian reversible jump Markov chain Monte Carlo

International audienceConstraining the past seismic activity and the slip-rates of faults over several millennials is crucial for seismic hazard assessment. Chlorine 36 (36 Cl) in situ produced cosmogenic nuclide is increasingly used to retrieve past earthquakes histories on seismically exhumed limestone normal fault-scarps. Following Schlagenhauf et al., (2010) modelling approach, we present a new methodology to retrieve the exhumation history based on a Bayesian transdimensional inversion of the 36 Cl data. This procedure uses the reversible jump Markov chains Monte-Carlo algorithm (RJ-MCMC, Green 1995) which enables 1-exploring the parameter space (number of events, age and slip of the events), 2-finding the most probable scenarios, and 3- precisely quantifying the associated uncertainties. Through a series of synthetic tests, the algorithm revealed a great capacity to constrain event slips and ages in a short computational time (several days) with a precision that can reach 0.1 ky and 0.5 m for the age and slip ofexhumation event, respectively. In addition, our study show that the amount of 36 Cl accumulated when the sampled fault-plane was still buried under the colluvial wedge, prior its exhumation, might represents up to 35 % of the total 36 Cl. This contribution can be accurately 25 determined with a depth profile that strongly increases the precision of the exhumation scenario

Unmanned aerial systems (UAS) operators’ accuracy and confidence of decisions: Professional pilots or video game players?

Unmanned Aerial Systems (UAS) operations have outpaced current training regimes resulting in a shortage of qualified UAS pilots. Three potential UAS operator groups were explored for suitability (i.e. video game players [VGP]; private pilots; professional pilots) and examined to assess levels of accuracy, confidence and confidence-accuracy judgements (W-S C-A) during a simulated civilian cargo flight. Sixty participants made 21 decision tasks, which varied across three levels of danger/risk. Scales of Tolerance of Ambiguity, Decision Style and NEO-PIR were also completed. Professional pilots and VGPs exhibited the highest level of decision confidence, with VGPs maintaining a constant and positive W-S C-A relationship across decision danger/risk. As decision danger/risk increased, confidence, accuracy and W-S C-A decreased. Decision danger also had a role to play in the confidence expressed when choosing to intervene or rely on automation. Neuroticism was negatively related, and conscientiousness positively related, to confidence. Intolerance of ambiguity was negatively related to W-S C-A. All groups showed higher levels of decision confidence in decisions controlled by the UAS in comparison to decisions where the operator manually intervened. VGPs display less overconfidence in decision judgements. Findings support the idea that VGPs could be considered a resource in UAS operation

Handling Qualities Assessment of a Pilot Cueing System for Autorotation Maneuvers

This paper details the design and limited flight testing of a preliminary system for visual pilot cueing during autorotation maneuvers. The cueing system is based on a fully-autonomous, multi-phase autorotation control law that has been shown to successfully achieve autonomous autorotation landing in unmanned helicopters. To transition this control law to manned systems, it is employed within a cockpit display to drive visual markers which indicate desired collective pitch and longitudinal cyclic positions throughout the entire maneuver, from autorotation entry to touchdown. A series of simulator flight experiments performed at University of Liverpool’s HELIFLIGHT-R simulator are documented, in which pilots attempt autorotation with and without the pilot cueing system in both good and degraded visual environments. Performance of the pilot cueing system is evaluated based on both subjective pilot feedback and objective measurements of landing survivability metrics, demonstrating suitable preliminary performance of the system

Understanding the legacy of widespread population translocations on the post-glacial genetic 2 structure of the European beech, Fagus sylvatica L.

Aim  Human impacts have shaped species ranges throughout the Holocene. The putative native range of beech, Fagus sylvatica, in Britain was obscured by its late post-glacial arrival and subsequent extensive management. We sought to differentiate the interacting effects of post-glacial colonization and anthropic impacts on the current genetic structure and diversity of beech by contrasting phylogeographic signals from putatively natural and translocated populations.  Location  Samples were obtained from 42 sites throughout Great Britain.  Methods  Chloroplast and nuclear microsatellite marker data were interpreted alongside palynological, historical and anecdotal evidence. Genetic structure was analysed using individual-based Bayesian assignment methods and colonization history was analysed using an approximate Bayesian computation framework.  Results  Phylogeographic patterns suggested contemporary forests originated from putative native south-eastern populations. High haplotypic diversity was found near the entry point of beech into Britain. Cryptic signals of isolation-by-distance persisted in the putative native range, together with higher levels of gene diversity in nuclear markers. Weak regional nuclear genetic structure suggested high levels of contemporary gene flow throughout the country.  Main conclusions  Genetic patterns driven by natural colonization persist despite widespread anthropic intervention. Forests in northerly regions were established from forests in the putative native range, diminishing the credibility of any present boundary between the native and non-native range of beech in Britain

Isolation of polymorphic microsatellites in the stemless thistle (Cirsium acaule) and their utility in other Cirsium species

The genus Cirsium includes species with both widespread and restricted geographical distributions, several of which are serious weeds. Nine polymorphic microsatellite loci were isolated from the stemless thistle Cirsium acaule. Eight were polymorphic in C. acaule, six in C. arvense and seven in C. heterophyllum. One locus monomorphic in C. acaule showed polymorphism in C. heterophyllum. The mean number of alleles per locus was 4.1 in C. acaule, 6.2 in C. arvense and 2.9 in C. heterophyllum. These nine loci were also amplified in C. eriophorum and C. vulgare, suggesting that these markers may be of use throughout the genus