Search

Among model checking tools, the behaviour of a system is often formalized as a transition system with atomic propositions associated with states (Kripke structure). In current modeling languages, transitions are usually specified as updates of the system's variables to be performed when certain conditions are satisfied. However, such a low-level representation makes the description of complex transformations difficult, in particular in the presence of structured data. We present Objective/MC, a high-level language with imperative semantics for modeling finite-state systems. The language features are selected with the aim of enabling the translation of models into compact transition systems, amenable to efficient verification via model checking. To this end, we have developed a compiler of our high-level language into the modeling language of the PRISM probabilistic model checker. One of the main characteristics of the language is that it makes a very different treatment of global and local variables. It is assumed that global variables are actually the variables that describe the state of the modeled system, whereas local variables are only used to ease the specification of the system's internal mechanisms. In this paper, we give a complete formal definition of the language, its type system and static analyses, of the transformations to be performed at the level of the Control Flow Graph for the pruning of local variables, and of the PRISM code generation. [ABSTRACT FROM AUTHOR]

Background and aims: In the Mediterranean basin, reduction in cloudiness owing to climate change is expected to enhance solar ultraviolet (UV) levels and to decrease rainfall over the coming years, which would be accompanied by more frequent and intense wildfires. The aim of the present study was to investigate the role of solar UV-A and UV-B radiation in C and N pools of a Mediterranean shrubland and whether drier conditions could alter this role before and after a fire.Methods: Over a three-year field experiment, 18 plots of 9 m2 were subjected to three UV conditions (UV-A + UV-B exclusion, UV-B exclusion or near-ambient UV-A + UV-B exposure) combined with two rainfall regimes (natural or reduced rainfall). Several parameters related to C and N cycles in the soil and in the leaves and litter of two dominant plant species (Arbutus unedo and Phillyrea angustifolia) were measured before and after an experimental fire.Results: UV-A exposure increased soil moisture throughout the study period, as well as respiration before the fire. The additional presence of UV-B decreased β-glucosidase activity at 5-10 cm depth and soil respiration and pH. UV-B exposure also raised leaf C concentration in P. angustifolia and δ15N values in A. unedo. Reduced rainfall often emphasized the opposite effects of UV-A and UV-B on the studied parameters. After the fire, most of the UV and rainfall effects were lost.Conclusion: UV-A exposure seems to stimulate soil biological activity and, thus, C and N turn-over, while the effect of UV-B would be the opposite. At least in the short term, the “homogenizing influence” of fire would probably have a stronger effect on the C and N cycles than the expected changes in UV and rainfall levels. [ABSTRACT FROM AUTHOR]

The reutilization of paper mill sludge as filler/reinforcement of polypropylene composites has been evaluated. The results show that the increasing content of sludge in composites resulted in materials with higher Young's modulus, although with lower tensile strength and deformation at break. Thus, in composites submitted to tensile stress paper mill sludge behaved mainly as filler. On the contrary, when materials were submitted to flexural stresses sludge worked partially as reinforcement. The addition of a coupling agent enhanced the fiber-matrix interface. As a result, composite materials with improved mechanical properties, either to tensile, flexural and impact tests were obtained. Considering the mechanical properties of the materials obtained, the substitution of traditional mineral fillers by paper mill sludge is a feasible alternative for composites used in low mechanical demand applications. [ABSTRACT FROM AUTHOR]

Seasonal fluctuations in the methane fluxes in the soil–atmosphere system were determined for gray forest soils of Central Russia. Consumption of atmospheric methane was found to exceed methane emission in gray forest soils under forest and in the agrocenosis. The average annual rates of atmospheric methane consumption by the soil under forest and in the agrocenosis were 0.026 and 0.008 mg C-CH4/(m2 h), respectively. The annual rate of atmospheric methane oxidation in the gray forest soils of Moscow oblast was estimated to be 0.68 kton. Seasonal fluctuations in the methane oxidation activity were due to changes in the hydrothermal conditions and in the reserves of readily decomposable organic matter and mineral nitrogen, as well as to changes in the activity of methane oxidizers. [ABSTRACT FROM AUTHOR]