Some effects of system information in instructions for use

An experiment was carried out to investigate whether it is useful to add system information to procedural information in instructional text. It was assumed that readers of instructions construct both a procedural and a system mental model, and that the latter enables the readers to infer possible missing information in procedural instructions. Moreover, it was assumed that system information would increase the cognitive load during reading and practicing, and that it would affect the appreciation of the instructions as well as the self-efficacy of the reader. The participants in the experiment read instructions and practiced with a fictitious machine before performing a number of tasks and answering a questionnaire. The results indicate that system information increased the cognitive load during reading and decreased self-efficacy, while the instructional text with system information was judged as more difficult. The effect on performance is limited: system information leads to faster performance for correctly completed tasks

Weak Order on Complete Quadrics

Using an action of the Richardson-Springer monoid on involutions, we study the weak order on the variety of complete quadrics. Maximal chains in the poset are explicitly determined. Applying results of Brion, our calculations describe certain cohomology classes in the complete flag variety.Comment: Some typos of the earlier version are fixed, a new section adde

The semiclassical propagator in field theory

We consider scalar field theory in a changing background field. As an example we study the simple case of a spatially varying mass for which we construct the semiclassical approximation to the propagator. The semiclassical dispersion relation is obtained by consideration of spectral integrals and agrees with the WKB result. Further we find that, as a consequence of localization, the semiclassical approximation necessarily contains quantum correlations in momentum space.Comment: Minor revisions, final version to be published in PLB. 10 pages and 3 figure

Making sense of step-by-step procedures

Procedural instructions that consist of only a sequence of steps will probably be executable, but nevertheless ¿meaningless¿ to users of technical devices. The paper discusses three features that can make procedural instructions more meaningful: adding functional coordinating information, adding information about the use of the technical device in real life, and adding operational information about how the device works. The research literature supports the effectiveness of the first feature, but offers little evidence that real life elements enhance understanding of instructions. As for operational information, the research suggests that users are willing to read it, and that it contributes to better understanding and performance in the long term, but only if it is closely related to the procedure. As a conclusion, we propose a theoretical framework that assumes three levels of mental representation of instructions: syntactical, semantic, and situationa

Attractor non-equilibrium stationary states in perturbed long-range interacting systems

Isolated long-range interacting particle systems appear generically to relax to non-equilibrium states ("quasi-stationary states" or QSS) which are stationary in the thermodynamic limit. A fundamental open question concerns the "robustness" of these states when the system is not isolated. In this paper we explore, using both analytical and numerical approaches to a paradigmatic one dimensional model, the effect of a simple class of perturbations. We call them "internal local perturbations" in that the particle energies are perturbed at collisions in a way which depends only on the local properties. Our central finding is that the effect of the perturbations is to drive all the very different QSS we consider towards a unique QSS. The latter is thus independent of the initial conditions of the system, but determined instead by both the long-range forces and the details of the perturbations applied. Thus in the presence of such a perturbation the long-range system evolves to a unique non-equilibrium stationary state, completely different to its state in absence of the perturbation, and it remains in this state when the perturbation is removed. We argue that this result may be generic for long-range interacting systems subject to perturbations which are dependent on the local properties (e.g. spatial density or velocity distribution) of the system itself.Comment: 16 pages, 12 figure

The nef cone volume of generalized Del Pezzo surfaces

We compute a naturally defined measure of the size of the nef cone of a Del Pezzo surface. The resulting number appears in a conjecture of Manin on the asymptotic behavior of the number of rational points of bounded height on the surface. The nef cone volume of a Del Pezzo surface Y with (-2)-curves defined over an algebraically closed field is equal to the nef cone volume of a smooth Del Pezzo surface of the same degree divided by the order of the Weyl group of a simply-laced root system associated to the configuration of (-2)-curves on Y. When Y is defined over a non-closed field of characteristic 0, a similar result holds, except that the associated root system is no longer necessarily simply-laced.Comment: v2, 25 pages; major revision containing additional results; comments welcom