167 research outputs found

    A pure jump Markov process with a random singularity spectrum

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    We construct a non-decreasing pure jump Markov process, whose jump measure heavily depends on the values taken by the process. We determine the singularity spectrum of this process, which turns out to be random and to depend locally on the values taken by the process. The result relies on fine properties of the distribution of Poisson point processes and on ubiquity theorems.Comment: 20 pages, 4 figure

    Feeding the Cities and Greenhouse Gas Emissions - Beyond the Food Miles Approach

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    In this paper, we study the impact of urbanization on the location of agricultural production and the GHG emissions related to transportation activities. We develop an economic geography model where the location of agricultural activities and urban population are endogenous. We show that increasing agricultural yields induce the spatial concentration of agricultural production in the least urbanized region if agricultural transport costs are relatively low and in the most urbanized region otherwise. In addition, interregional trade in agricultural commodities is desirable to reduce GHG emissions, except when urban population is equally split between cities. However, the market may induce too much agglomeration of agricultural production when yields are high and when collection costs are low.Urbanization, agriculture location, transport, Environmental Economics and Policy, Food Security and Poverty, Q10, Q54, R12,

    Parallel Linear Multigrid Algorithms Applied to the Acceleration of Compressible Flows

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    The interest in unstructured meshes for Computational Fluid Dynamics (CFD) applications appears to be increansingly important in the industrial community. Industrial applications require the numerical simulation of complex flows (i.e. the underlying flows exhibit localized high variations of physical quantities) around or within complex geometries. Unstructured meshes are particularly well suited to these kinds of simulation due to their ability in accurately discretizing complex computational domains and, to their flexibility in dynamically refining and derefining, or deforming, in order to match the underlying flow features. Concerning flow solvers, the main question appears to be the lack of efficiency demonstrated by unstructured mesh solvers compared to structured ones. Many efficient methods developed in the structured context are not easily extensible to unstructured meshes and much research work has yet to be done in this direction. During the last ten years, several such works have demonstrated that multigrid principles can yield robust and efficient unstructured mesh solvers (see for example Lallemand {\it et al.}\cite{Lal92}, Koobus {\it et al.}\cite{Lal94}, Carré\cite{Car97}, Mavriplis {\it et al.}\cite{Mav87}-\cite{Mav88}-\cite{Mav95}). In this report, we describe ongoing research activities aiming at the construction of efficient and robust unstructured multigrid solvers for complex 2D and 3D flow simulations. Both academic and industrial aspects are considered

    Modelling the impact of beliefs and communication on attitude dynamics : a cognitive agent-based approach

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    In the context of military training for stabilization operation of a crisis zone with civilian population, understanding the formation of attitude and its dynamics is a key issue. This paper presents a multi-agent model for simulating attitude formation and change based on individual's perception of information and its diffusion through communication. We represent the attitude as object-evaluation associations of varying strength proposed by Fazio [1]. Individuals observe military operations. They exchange and revise beliefs about social objects depending on multiple criteria deriving from social psychology theories. They compute their attitude value based on analytic assessment of these beliefs. We illustrate, through several simulation experiments, the role of communication on attitude dynamics

    Design, Manufacture and Wind Tunnel Test of a Modular FishBAC Wing with Novel 3D Printed Skins

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    This paper introduces a new modular Fish Bone Active Camber morphing wing with novel 3D printed skin panels. These skin panels are printed using two different Thermoplastic Polyurethane (TPU) formulations: a soft, high strain formulation for the deformable membrane of the skin, reinforced with a stiffer formulation for the stringers and mounting tabs. Additionally, this is the first FishBAC device designed to be modular in its installation and actuation. Therefore, all components can be removed and replaced for maintenance purposes without having to remove or disassemble other parts. A 1 m span, 0.27 m chord morphing wing with a 25% chord FishBAC was built and tested mechanically and in a low-speed wind tunnel. Results show that the new design is capable of achieving the same large changes in airfoil lift coefficient (approximate ΔCL≈0.55) with a low drag penalty seen in previous FishBAC work, but with a much simpler, practical and modular design. Additionally, the device shows a change in the pitching moment coefficient of ΔCM≈0.1, which shows the potential that the FishBAC has as a control surface

    Gingival inflammation, enamel defects, and tooth sensitivity in children with amelogenesis imperfecta: a case-control study

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    Gingival conditions and tooth sensitivity of young patients with amelogenesis imperfecta lack in depth studies. This case-control study aimed to compare (1) the gingival inflammation, the presence of enamel defects, and tooth sensitivity in young patients with and without amelogenesis imperfecta and (2) to investigate if any difference exists between subtypes of amelogenesis imperfecta. Methodology: We compared forty-two participants with amelogenesis imperfecta with forty-two controls matched for age, gender, and the number of examined sites. Based on interview, clinical examination, and intraoral photography, we collected data on periodontal conditions, enamel defects and the presence of tooth sensitivity. Comparison tests were performed to investigate if any difference existed between cases and controls; and among cases, between the different subtypes of amelogenesis imperfecta. We performed a post-hoc analysis for any significant difference observed. Results: We observed more gingival inflammation, enamel defects and tooth sensitivity among cases (all p<0.05). Participants with hypocalcified amelogenesis imperfecta had more gingival inflammation, enamel defects, and tooth sensitivity than patients with the hypoplastic and hypomature subtypes (all p<0.05). After adjustment for dental plaque, gingival inflammation was associated with the presence of amelogenesis imperfecta (OR (95%CI) = 1.14 (1.05; 1.24). p<0.01). Conclusion: Gingival inflammation, enamel defect and tooth sensitivity are more frequently observed among young patients with amelogenesis imperfecta, and more specifically among children with the hypocalcified subtype

    COMBINED CONDUCTIVE-RADIATIVE HEAT TRANSFER ANALYSIS IN COMPLEX GEOMETRY USING THE MONTE CARLO METHOD

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    Deterministic methods are commonly used to solve the heat balance equation in three-dimensional (3D) geometries. This article presents a preliminary study to the use of a stochastic method for the computation of the temperature in complex 3D geometries where the combined conductive and radiative heat transfers are coupled in the porous solid phase. The Monte Carlo algorithm and its results are validated by a comparison with the results obtained with a conventional finite-volume method

    Twenty-year trends in the prevalence of modifiable cardiovascular risk factors in young acute coronary syndrome patients hospitalized in Switzerland

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    AIMS Modifiable cardiovascular risk factors (RFs) play a key role in the development of coronary artery disease. We evaluated 20-year trends in RF prevalence among young adults hospitalized with acute coronary syndromes (ACS) in Switzerland. METHODS AND RESULTS Data were analysed from the Acute Myocardial Infarction in Switzerland (AMIS) Plus registry from 2000 to 2019. Young patients were defined as those aged <50 years. Among 58 028 ACS admissions, 7073 (14.1%) were young (median 45.6 years, IQR 42.0-48.0), of which 91.6% had at least one modifiable RF and 59.0% had at least two RFs. Smoking was the most prevalent RF (71.4%), followed by dyslipidaemia (57.3%), hypertension (35.9%), obesity (21.7%), and diabetes (10.1%). Compared with older patients, young patients were more likely to be obese (21.7% vs. 17.4%, P < 0.001) and active smokers (71.4% vs. 33.9%, P < 0.001). Among young patients, between 2000 and 2019, there was a significant increase in the prevalence of hypertension from 29.0% to 51.3% and obesity from 21.2% to 27.1% (both Ptrend < 0.001) but a significant decrease in active smoking from 72.5% to 62.5% (Ptrend = 0.02). There were no significant changes in the prevalence of diabetes (Ptrend = 0.32) or dyslipidaemia (Ptrend = 0.067). CONCLUSION Young ACS patients in Switzerland exhibit a high prevalence of RFs and are more likely than older patients to be obese and smokers. Between 2000 and 2019, RF prevalence either increased or remained stable, except for smoking which decreased but still affected approximately two-thirds of young patients in 2019. Public health initiatives targeting RFs in young adults in Switzerland are warranted
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