9,675 research outputs found
Verification-guided modelling of salience and cognitive load
Well-designed interfaces use procedural and sensory cues to increase the cognitive salience of appropriate actions. However, empirical studies suggest that cognitive load can influence the strength of those cues. We formalise the relationship between salience and cognitive load revealed by empirical data. We add these rules to our abstract cognitive architecture, based on higher-order logic and developed for the formal verification of usability properties. The interface of a fire engine dispatch task from the empirical studies is then formally modelled and verified. The outcomes of this verification and their comparison with the empirical data provide a way of assessing our salience and load rules. They also guide further iterative refinements of these rules. Furthermore, the juxtaposition of the outcomes of formal analysis and empirical studies suggests new experimental hypotheses, thus providing input to researchers in cognitive science
Consequences of energy conservation in relativistic heavy-ion collisions
Complete characterization of particle production and emission in relativistic
heavy-ion collisions is in general not feasible experimentally. This work
demonstrates, however, that the availability of essentially complete
pseudorapidity distributions for charged particles allows for a reliable
estimate of the average transverse momenta and energy of emitted particles by
requiring energy conservation in the process. The results of such an analysis
for Au+Au collisions at sqrt{s_{NN}}= 130 and 200 GeV are compared with
measurements of mean-p_T and mean-E_T in regions where such measurements are
available. The mean-p_T dependence on pseudorapidity for Au+Au collisions at
130 and 200 GeV is given for different collision centralities.Comment: 8 pages, 8 figures, Submitted to Phys. Rev.
Specifying the Caltech asynchronous microprocessor
The action systems framework for modelling parallel programs is used to formally specify a microprocessor. First the microprocessor is specified as a sequential program. The sequential specification is then decomposed and refined into a concurrent program using correctness-preserving program transformations. Previously this microprocessor has been specified at Caltech, where an asynchronous circuit for the microprocessor was derived from the specification. We propose a specification strategy that is based on the idea of spatial decomposition of the program variable space
Overview of Solid Target Studies for a Neutrino Factory
The UK proĀgramme of high power tarĀget deĀvelĀopĀments for a NeuĀtriĀno FacĀtoĀry is cenĀtred on the study of high-Z maĀteĀriĀals (tungĀsten, tanĀtaĀlum). A deĀscripĀtion of lifeĀtime shock tests on canĀdiĀdate maĀteĀriĀals is given as part of the reĀsearch into a solid tarĀget soĀluĀtion. A fast high curĀrent pulse is apĀplied to a thin wire of the samĀple maĀteĀriĀal and the lifeĀtime meaĀsured from the numĀber of pulsĀes beĀfore failĀure. These meaĀsureĀments are made at temĀperĀaĀtures up to ~2000 K. The stress on the wire is calĀcuĀlatĀed using the LS-DYĀNA code and comĀpared to the stress exĀpectĀed in the real NeuĀtriĀno FacĀtoĀry tarĀget. It has been found that tanĀtaĀlum is too weak to susĀtain proĀlonged stress at these temĀperĀaĀtures but a tungĀsten wire has reached over 26 milĀlion pulsĀes (equivĀaĀlent to more than ten years of opĀerĀaĀtion at the NeuĀtriĀno FacĀtoĀry). An acĀcount is given of the opĀtiĀmiĀsaĀtion of secĀondary pion proĀducĀtion from the tarĀget and the isĀsues reĀlatĀed to mountĀing the tarĀget in the muon capĀture solenoid and tarĀget staĀtion are disĀcussed
The composition of Event-B models
The transition from classical B [2] to the Event-B language and method [3] has seen the removal of some forms of model structuring and composition, with the intention of reinventing them in future. This work contributes to thatreinvention. Inspired by a proposed method for state-based decomposition and refinement [5] of an Event-B model, we propose a familiar parallel event composition (over disjoint state variable lists), and the less familiar event fusion (over intersecting state variable lists). A brief motivation is provided for these and other forms of composition of models, in terms of feature-based modelling. We show that model consistency is preserved under such compositions. More significantly we show that model composition preserves refinement
Refinement Calculus, Lattices and Higher Order Logic
We show how to describe refinement calculus in a lattice theoretic framework. The predicate transformer lattice is built by pointwise extensions from the truth value lattice. A simple but very powerful statement language characterizes the monotonic predicate transformer lattice. We show how to formalize the calculus in higher order logic. We also show how to express data refinement in this framework. A theorem of data refinement with stuttering is proved, to illustrate the algebraic nature of reasoning in this framework
Refinement of Parallel and Reactive Programs
We show how to apply the refinement calculus to stepwise refinement of parallel and reactive programs. We use action systems as our basic program model. Action systems are sequential programs which can be implemented in a parallel fashion. Hence refinement calculus methods, originally developed for sequential programs, carry over to the derivation of parallel programs. Refinement of reactive programs is handled by data refinement techniques originally developed for the sequential refinement calculus. We exemplify the approach by a derivation of a mutual exclusion algorithm
Predicate Transformers and Higher Order Logic
Predicate transformers are formalized in higher order logic. This gives a basis for mechanized reasoning about total correctness and refinement of programs. The notions of program variables and logical variables are explicated in the formalization. We show how to describe common program constructs, such as assignment statements, sequential and conditional composition, iteration, recursion, blocks and procedures with parameters, axe described as predicate transformers in this framework. We also describe some specification oriented constructs, such as assert statements, guards and nondeterministic assignments. The monotonicity of these constructs over the lattice of predicates is proved, as well as the monotonicity of the statement constructors with respect to the refinement ordering on predicate transformers
Energy and system dependence of high- triggered two-particle near-side correlations
Previous studies have indicated that the near-side peak of high-
triggered correlations can be decomposed into two parts, the \textit{Jet} and
the \textit{Ridge}. We present data on the yield per trigger of the
\textit{Jet} and the \textit{Ridge} from , and collisions
at = 62.4 GeV and 200 GeV and compare data on the \textit{Jet}
to PYTHIA 8.1 simulations for . PYTHIA describes the \textit{Jet}
component up to a scaling factor, meaning that PYTHIA can provide a better
understanding of the \textit{Ridge} by giving insight into the effects of the
kinematic cuts. We present collision energy and system dependence of the
\textit{Ridge} yield, which should help distinguish models for the production
mechanism of the \textit{Ridge}.Comment: 4 pages, 6 figures, proceedings for Hot Quarks in Estes Park,
Colorad
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