A review of wildland fire spread modelling, 1990-present, 1: Physical and quasi-physical models

In recent years, advances in computational power and spatial data analysis (GIS, remote sensing, etc) have led to an increase in attempts to model the spread and behaviour of wildland fires across the landscape. This series of review papers endeavours to critically and comprehensively review all types of surface fire spread models developed since 1990. This paper reviews models of a physical or quasi-physical nature. These models are based on the fundamental chemistry and/or physics of combustion and fire spread. Other papers in the series review models of an empirical or quasi-empirical nature, and mathematical analogues and simulation models. Many models are extensions or refinements of models developed before 1990. Where this is the case, these models are also discussed but much less comprehensively.Comment: 31 pages + 8 pages references + 2 figures + 5 tables. Submitted to International Journal of Wildland Fir

Clone-Dependent Expression of Esca Disease Revealed by Leaf Metabolite Analysis

Grapevine trutk diseases, especially Esca, are of major concern since they gradually alter vineyards worldwide and cause heavy economic losses. The expression of Esca disease symptoms depends on several factors, including the grapevine cultivar. In this context, a possible clone-dependent expression of the Esca disease was studied. Two clones of ‘Chardonnay’ grown in the same plot were compared according to their developmental and physiological traits, metabolome, and foliar symptom expression. Analysis of their leaf metabolome highlighted differences related to symptom expression. Interestingly, the content of a few specific metabolites exhibited opposite variations in leaves of symptomatic shoots of clones 76 and 95. Altogether this study showed a clone-dependent expression of Esca disease in ‘Chardonnay’ and the relevance of GC-MS and 3D fluorescence methods to analyze the impact of the disease on the leaf metabolome

French Roadmap for complex Systems 2008-2009

This second issue of the French Complex Systems Roadmap is the outcome of the Entretiens de Cargese 2008, an interdisciplinary brainstorming session organized over one week in 2008, jointly by RNSC, ISC-PIF and IXXI. It capitalizes on the first roadmap and gathers contributions of more than 70 scientists from major French institutions. The aim of this roadmap is to foster the coordination of the complex systems community on focused topics and questions, as well as to present contributions and challenges in the complex systems sciences and complexity science to the public, political and industrial spheres

Towards a robust optimization of spot weld design in automotive structures

International audienceThe design of a resistance spot weld distribution for an automobile body-in-white has a strong impact not only on the global system performance but also on the robustness of this performance with respect to uncertainties due to assembly defects and fatigue failures. A quantitative methodology is presented that provides decision-making indicators that allow the analyst to insure a given level of system performance at the cost of performing a quality control of a limited number of welds coming off the assembly line as well as reinforcing a set of critical welds in order to improve the robustness to fatigue failure. In contrast with existing sample-based robustness analyses, the proposed methodology gives visibility to the compromise between improved robustness and higher assembly and quality control costs. In other words, this methodology provides a tool to guide the analyst in the next step to improving robustness while giving an estimation to the cost of the predicted improvement. All examples are presented on a full BIW structure (1,000,000 dofs and 6,500 spot welds

Zero reflections by a 1D Acoustic Black Hole termination using thermally controlled damping

International audienceThe design of lightweight and stiff structures with attractive vibration damping properties is a major issue in mechanical engineering. The insertion of Acoustic Black Holes (ABH) in a beam is a technique that consists in locally reducing its thickness at the end and coating it with a visco-elastic film. The reflection coefficient of the resulting system decreases with frequency and displays typical arches which can exactely reach zero when the amount of losses is well adjusted, reaching the critical coupling condition. However, the precise amount of added damping is very difficult to tune by using classical visco-elastic layers. It is here proposed to control it by using a thermal active system acting in a shape memory polymer (SMP). In this manner, the damping and stiffness profiles become tunable via a given thermal gradient which leads to create an enhanced ABH (eABH) that can be tuned in real time, so that the critical coupling can be reached. The objective of the paper is to demonstrate numerically and experimentally the capability of an eABH to achieve exact zero reflections using precise control of temperature gradients

Influence of ocean salinity stratification on the tropical Atlantic Ocean surface

International audienceThe tropical Atlantic Ocean receives an important freshwater supply from river runoff and from precipitation in the intertropical convergence zone. It results in a strong salinity stratification that may influence vertical mixing, and thus sea surface temperature (SST) and air-sea fluxes. The aim of this study is to assess the impact of salinity stratification on the tropical Atlantic surface variables. This is achieved through comparison among regional 1/4∘ coupled ocean-atmosphere simulations for which the contribution of salinity stratification in the vertical mixing scheme is included or discarded. The analysis reveals that the strong salinity stratification in the northwestern tropical Atlantic induces a significant increase of SST (0.2 ∘C-0.5 ∘C) and rainfall (+ 19%) in summer, hereby intensifying the ocean-atmosphere water cycle, despite a negative atmospheric feedback. Indeed, the atmosphere dampens the oceanic response through an increase in latent heat loss and a reduction of shortwave radiation reaching the ocean surface. In winter, the impacts of salinity stratification are much weaker, most probably because of a deeper mixed layer at this time. In the equatorial region, we found that salinity stratification induces a year-round shoaling of the thermocline, reinforcing the cold tongue cool anomaly in summer. The concept of barrier layer has not been identified as relevant to explain the SST response to salinity stratification in our region of interest

Enhanced acoustic black holes (EABH) based on tuned damping properties obtained by thermal control

International audienceThe design of lightweight and stiff structures with attractive vibration damping properties is a major issue in mechanical engineering. The insertion of Acoustic Black Holes (ABH) is an innovative technique that consists in locally reducing the thickness of the stucture<br&gtand coating it with a viscoelastic film. In the particular case where the damping layer provides a perfect adjustment of the losses, the reflection coefficient R of the resulting system is zero at the resonance of a trapped mode localized in the ABH profile. This phenonemon is<br&gtreached when the critical coupling conditions are fulfilled. However, the precise amount of losses is particularly difficult to tune by using only classical viscoelastic layers. It is here proposed to control it by using a thermal active system acting in a shape memory polymer (SMP).<br&gtThe goal of the paper is to investigate several enhanced ABH (eABH) in beams for which the damping and the stiffness are controlled by a thermal profile. For each eABH configuration, the trajectory of the zeros of R is studied in order to approach the critical coupling conditions

Reflection coefficients of Enhanced Acoustic Black Holes at a beam termination

International audienceThe design of lightweight and stiff structures with high vibration damping properties is an important issue in mechanical engineering. The insertion of Acoustic Black Holes (ABH) in a flat panel or in a beam termination is an innovative technique for passive structural vibration damping without added mass. ABH consist in local heterogeneities of the stiffness and the damping and are known as efficient absorbers forflexural waves above their cut-on frequency. The goal of the paper is to identify and to push the current limitations of this existing strategy by developing ”enhanced acoustic black holes” (eABH) absorbers based on the integration of thermal adaptive systems. The capability of such techniques to enhance the control of the flexural rigidity and the local damping is investigated numerically. The reflection coefficients, R, of several architectures of ABH beam termination are computed using the Impedance Matrix method. Such a method is adapted to the accurate computation of R of a structural wave guide with varying properties. Comparing R of several architectures allows us to discuss the potentialities of such eABH