SaBRe: load-time selective binary rewriting

Binary rewriting consists in disassembling a program to modify its instructions. However, existing solutions suffer from shortcomings in terms of soundness and performance. We present SaBRe, a load-time system for selective binary rewriting. SaBRe rewrites specific constructs—particularly system calls and functions—when the program is loaded into memory, and intercepts them using plugins through a simple API. We also discuss the theoretical underpinnings of disassembling and rewriting. We developed two backends—for x86_64 and RISC-V—which were used to implement three plugins: a fast system call tracer, a multi-version executor, and a fault injector. Our evaluation shows that SaBRe imposes little overhead, typically below 3%.

     

Experimental study of laminar flames obtained by the homogenization of three forest fuels

This work aims to improve the understanding of the parameters involved in the burning of vegetative fuels. As the role of the surface-to-volume ratio is already known, we focused on the influence of other parameters. Three Mediterranean species (Pinus pinaster, Erica arborea and Cistus monspeliensis) were crushed in order to decrease the surface-to-volume ratio effects. The burning of these fuel samples produces unsteady, axisymmetric, non-premixed, laminar flames. The thermal properties and the mass loss of the crushed fuels, the distribution of temperature inside the sample and in the flame, the gases released by the fuels and the flame geometry were investigated. Thanks to these experimental data, the influence of the different fuel properties was underlined. We observed that the mass burning rate of the samples mainly controls the flame dynamics. However, the combustion kinetics in the flame depends on the degradation gases released by the fuels: the reaction zone is shifted and the flame height is changed. It appears that the composition of the degradation gases has to be taken into account to improve forest fire modeling.     

Multi-scale simulations of the thermal degradation of thin wooden plates: Evaluation of two kinetic mechanisms

This study evaluates two kinetic mechanisms to predict, on matter-level and material-level scales, the thermal degradation of thin plates of oak and eucalyptus as representing vegetative fuel involved in wildfires. The lumped mechanism considers four successive steps, whereas the simplified one includes two steps. The kinetic parameters of these mechanisms were identified with thermogravimetric analysis in air for heating rates between 2 and 30 °C min^?1. On the matter-level scale, kinetic mechanisms were tested for heating rates inside and outside the parameters optimization range. The simulations of the mass loss were close to the experimental data. The lumped mechanism gave better results than the simplified one. On the material-level scale, the mass loss and temperature recorded during thermal degradation of thin wooden plates, with a heating cone, were compared to simulations performed with GPYRO. When only the gasification stage occurred, both mechanisms predicted results close to the experimental data. When char oxidation occurred, the beginning of the gasification stage was well predicted, whereas some differences appeared during the transition between the gasification and char oxidation stages. The performance of both mechanisms indicates that a two-step mechanism is capable of modeling the thermal degradation of thin wooden plates on a material scale.