223 research outputs found

    Curvature-direction measures of self-similar sets

    Full text link
    We obtain fractal Lipschitz-Killing curvature-direction measures for a large class of self-similar sets F in R^d. Such measures jointly describe the distribution of normal vectors and localize curvature by analogues of the higher order mean curvatures of differentiable submanifolds. They decouple as independent products of the unit Hausdorff measure on F and a self-similar fibre measure on the sphere, which can be computed by an integral formula. The corresponding local density approach uses an ergodic dynamical system formed by extending the code space shift by a subgroup of the orthogonal group. We then give a remarkably simple proof for the resulting measure version under minimal assumptions.Comment: 17 pages, 2 figures. Update for author's name chang

    Delays in IP routers, a Markov model

    Get PDF
    Delays in routers are an important component of end-to-end delay and therefore have a significant impact on quality of service. While the other component, the propagation time, is easy to predict as the distance divided by the speed of light inside the link, the queueing delays of packets inside routers depend on the current, usually dynamically changing congestion and on the stochastic features of the flows. We use a Markov model taking into account the distribution of the size of packets and self-similarity of incoming flows to investigate their impact on the queueing delays and their dynamics

    Modelling and Analysing Mixed Reality Applications

    Get PDF
    International audienceMixed reality systems overlay real data with virtual information in order to assist users in their current task. They generally combine several hardware components operating at different time scales, and software that has to cope with these timing constraints. MIRELA, for MIxed REality LAnguage, is a framework aimed at modelling, analysing and implementing systems composed of sensors, processing units, shared memories and rendering loops, communicating in a well-defined manner and submitted to timing constraints. The framework is composed of (i) a language allowing a high level, and partially abstract, specification of a concurrent real–time system, (ii) the corresponding semantics, which defines the translation of the system to concrete networks of timed automata, (iii) a methodology for analysing various real-time properties, and (iv) an implementation strategy. We present here a summary of several of our papers about this framework, as well as some recent extensions concerning probability and non–deterministic choices

    The impact of unemployment and non-standard forms of employment on the housing autonomy of young adults

    Get PDF
    Young people are facing challenges in transitioning to housing autonomy because of changes in labour market conditions in recent years. This article explores the effects of youth unemployment and non-standard employment on the likelihood of leaving the parental home. We adopt a dynamic modelling approach, and use data from a large longitudinal British survey covering the years 2009-2014. We find that unemployment and part-time work, but not the duration of the contract, have a negative effect on the likelihood of obtaining housing autonomy. We also find that past as well as anticipated unemployment have significant negative effects, which suggests that the decision about whether to move out depends on the individual’s longer-term labour market trajectory. The analysis also reveals gender differences in part-time work, but not in unemployment once we take into account unobserved time-invariant heterogeneity

    Comparison of simulation and analytical models for the distribution of a group of agents moving in random directions

    Get PDF
    This study focused on simulation and analytical models of a multidimensional random walk of many agent

    Dirofilaria spp. And angiostrongylus vasorum: Current risk of spreading in central and northern europe

    Get PDF
    In the past few decades, the relevance of Dirofilaria immitis and Dirofilaria repens, causing cardiopulmonary and subcutaneous dirofilariosis in dogs and cats, and of Angiostrongylus vasorum, causing canine angiostrongylosis, has steadily increased in Central and Northern Europe. In this review, a summary of published articles and additional reports dealing with imported or autoch-thonous cases of these parasites is provided for Central (Austria, Czechia, Germany, Hungary, Lux-emburg, Poland, Slovakia, Slovenia, and Switzerland) and Northern (Denmark, Finland, Iceland, Norway, and Sweden) Europe. Research efforts focusing on Dirofilaria spp. and A. vasorum have varied by country, and cross-border studies are few. The housing conditions of dogs, pet move-ments, the spread of competent vectors, and climate change are important factors in the spread of these nematodes. Dogs kept outside overnight are a major factor for the establishment of Dirofilaria spp. However, the establishment of invasive, diurnal, synanthropic, competent mosquito vectors such as Aedes albopictus may also influence the establishment of Dirofilaria spp. The drivers of the spread of A. vasorum remain not fully understood, but it seems to be influenced by habitats shared with wild canids, dog relocation, and possibly climatic changes; its pattern of spreading appears to be similar in different countries. Both Dirofilaria spp. and A. vasorum merit further monitoring and research focus in Europe
    corecore