Discrete-Event Analytic Technique for Surface Growth Problems

We introduce an approach for calculating non-universal properties of rough surfaces. The technique uses concepts of distinct surface-configuration classes, defined by the surface growth rule. The key idea is a mapping between discrete events that take place on the interface and its elementary local-site configurations. We construct theoretical probability distributions of deposition events at saturation for surfaces generated by selected growth rules. These distributions are then used to compute measurable physical quantities. Despite the neglect of temporal correlations, our approximate analytical results are in very good agreement with numerical simulations. This discrete-event analytic technique can be particularly useful when applied to quantification problems, which are known to not be suited to continuum methods.Comment: 4 pages, 7 figures, published 17 Feb. 200

Healthcare services managers: what information do they need and use?

Objectives: To gain insight into the information behaviour of healthcare services managers as they draw on information while engaged in decision making unrelated to individual patient care. Objectives – The purpose of this research project was to gain insight into the information behaviour of healthcare services managers as they use information while engaged in decision-making unrelated to individual patient care. Methods – This small-scale, exploratory, multiple case study used the critical incident technique in nineteen semi-structured interviews. Responses were analyzed using ‘Framework,’ a matrix-based content analysis system. Results – This paper presents findings related to the internal information that healthcare services managers need and use. Their decisions are influenced by a wide variety of factors. They must often make decisions without all of the information they would prefer to have. Internal information and practical experience set the context for new research-based information, so they are generally considered first. Conclusions – Healthcare services managers support decisions with both facts and value-based information. These results may inform both delivery of health library services delivery and strategic health information management planning. They may also support librarians who extend their skills beyond managing library collections and teaching published information retrieval skills, to managing internal and external information, teaching information literacy, and supporting information sharing

On computing fixpoints in well-structured regular model checking, with applications to lossy channel systems

We prove a general finite convergence theorem for "upward-guarded" fixpoint expressions over a well-quasi-ordered set. This has immediate applications in regular model checking of well-structured systems, where a main issue is the eventual convergence of fixpoint computations. In particular, we are able to directly obtain several new decidability results on lossy channel systems.Comment: 16 page

Solyanik estimates in harmonic analysis

Let $\mathcal{B}$ denote a collection of open bounded sets in $\mathbb{R}^n$, and define the associated maximal operator $M_{\mathcal{B}}$ by $$M_{\mathcal{B}}f(x) := \sup_{x \in R \in \mathcal{B}} \frac{1}{|R|}\int_R |f|.$$ The sharp Tauberian constant of $M_{\mathcal{B}}$ associated to $\alpha$, denoted by $C_{\mathcal{B}}(\alpha)$, is defined as $$C_{\mathcal{B}}(\alpha) := \sup_{E :\, 0 < |E| < \infty}\frac{1}{|E|}\big|\big\{x \in \mathbb{R}^n:\, M_{\mathcal{B}}\chi_E (x) > \alpha\big\}\big|.$$ Motivated by previous work of A. A. Solyanik, we show that if $M_{\mathcal{B}}$ is the uncentered Hardy-Littlewood maximal operator associated to balls, the estimate $$\lim_{\alpha \rightarrow 1^-}C_{\mathcal{B}}(\alpha) = 1$$ holds. Similar results for iterated maximal functions are obtained, and open problems in the field of Solyanik estimates are also discussed.Comment: 17 pages, 2 figures, minor typos corrected, to appear in Springer Proceedings in Mathematics & Statistic

On-line multiobjective automatic control system generation by evolutionary algorithms

Evolutionary algorithms are applied to the on- line generation of servo-motor control systems. In this paper, the evolving population of controllers is evaluated at run-time via hardware in the loop, rather than on a simulated model. Disturbances are also introduced at run-time in order to pro- duce robust performance. Multiobjective optimisation of both PI and Fuzzy Logic controllers is considered. Finally an on-line implementation of Genetic Programming is presented based around the Simulink standard blockset. The on-line designed controllers are shown to be robust to both system noise and ex- ternal disturbances while still demonstrating excellent steady- state and dvnamic characteristics

Electronic transport in strongly anisotropic disordered systems: model for the random matrix theory with non-integer beta

We study numerically an electronic transport in strongly anisotropic weakly disorderd two-dimensional systems. We find that the conductance distribution is gaussian but the conductance fluctuations increase when anisotropy becomes stronger. We interpret this result by random matrix theory with non-integer symmetry parameter beta, in accordance with recent theoretical work of K.A.Muttalib and J.R.Klauder [Phys.Rev.Lett. 82 (1999) 4272]. Analysis of the statistics of transport paramateres supports this hypothesis.Comment: 8 pages, 7 *.eps figure

Determinants of species richness patterns in the Netherlands across multiple taxonomic groups

We examined the species richness patterns of five different species groups (mosses, reptiles and amphibians, grasshoppers and crickets, dragonflies, and hoverflies) in the Netherlands (41,500 km2) using sampling units of 5 × 5 km. We compared the spatial patterns of species richness of the five groups using Spearman¿s rank correlation and used a stepwise multiple regression generalized linear modelling (GLM) approach to assess their relation with a set of 36 environmental variables, selected because they can be related to the several hypotheses on biodiversity patterns. Species richness patterns of the five groups were to a certain extent congruent. Our data suggest that environmental heterogeneity (in particular habitat heterogeneity) is one of the major determinants of variation in species richness within these five groups. We found that for taxonomic groups comprising a low number of species, our regression model explained more of the variability in species richness than for taxonomic groups with a large number of specie

Reduction and Realization in Toda and Volterra

We construct a new symplectic, bi-hamiltonian realization of the KM-system by reducing the corresponding one for the Toda lattice. The bi-hamiltonian pair is constructed using a reduction theorem of Fernandes and Vanhaecke. In this paper we also review the important work of Moser on the Toda and KM-systems.Comment: 17 page

Electronic transport through ballistic chaotic cavities: reflection symmetry, direct processes, and symmetry breaking

We extend previous studies on transport through ballistic chaotic cavities with spatial left-right (LR) reflection symmetry to include the presence of direct processes. We first analyze fully LR-symmetric systems in the presence of direct processes and compare the distribution w(T) of the transmission coefficient T with that for an asymmetric cavity with the same "optical" S matrix. We then study the problem of "external mixing" of the symmetry caused by an asymmetric coupling of the cavity to the outside. We first consider the case where symmetry breaking arises because two symmetrically positioned waveguides are coupled to the cavity by means of asymmetric tunnel barriers. Although this system is asymmetric with respect to the LR operation, it has a striking memory of the symmetry of the cavity it was constructed from. Secondly, we break LR symmetry in the absence of direct proceses by asymmetrically positioning the two waveguides and compare the results with those for the completely asymmetric case.Comment: 15 pages, 8 Postscript figures, submitted to Phys. Rev.

CFD modelling of a hospital ward: Assessing risk from bacteria produced from respiratory and activity sources

It has been identified that potentially pathogenic acteria, such as MRSA can be released from the skin during routine activities within hospital wards, such as bed-making, washing patients, dressing and walking. CFD is often used to study airflow patterns and ventilation regimes within hospitals, however such models tend not to consider these types of dispersal mechanisms and concentrate on respiratory transmission, using a point source at the mouth position. A zonal source is demonstrated to represent this release from activity within CFD simulations using both passive scalar and Lagrangian particle tracking. Sensitivity studies are carried out for point and zonal sources. The point source was found to not adequately represent the release of bacteria from a zone and therefore the zonal source is recommended to be used in conjunction with this type of source in order to simulate both respiratory and activity sources of bacteria