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Stochastic Petri nets (SPN) or Markov models (MC) are often more effective in the reliability analysis of discrete event systems. However, they present a problem of combinatorial explosion of the number of states when the systems present several interdependent components. This problem limits the use of the MC. The SPN is considered a Markov estimator, but it has a slow convergence in the calculations of stationary state probabilities. The continuous Petri nets (CPN) are developed to accelerate this convergence by capturing the SPN behaviour. This study considers three different Petri nets (PN) types. Simulations with the MC, SPN, and CPN, are presented and compared in different PN types. The obtained results show that the MC and the SPN have identical behaviour in the general case. Furthermore, the CPN exhibits identical behaviour in the first type, which is not the case in the other two types.

The fluidification of stochastic discrete event models is a more interesting method to overcome the problem of combinatorial explosion of states. It allows to relax the conditions of stochastic Petri nets to continuous Petri nets, in order to accelerate the slow convergence of stochastic simulations. In our study, we will study an example of a large manufacturing workshop, in order to give limitations of the direct fluidification which does not always lead to the same behaviour between the two models. Secondly, we propose a numerical approach called adaptive that devotes to the adaptation of the maximum speeds of crossing the transitions that is considered as functions depending on the time. Consequently, this approach shows an excellent convergence of the continuous model to the stochastic one whatever the type of network and whatever the initial marking.

Salinity is one of the major factors that limit tomato growth and productivity, causing morphological and physiological changes and impacting plant metabolism. Seaweed extracts can reduce these harmful effects. Therefore, in this study we examined the effect of Cystoseira tamariscifoliaextract (CTE) on NaCl stress tolerance in tomato plants. We assessed the effect of different concentrations of CTE on germination parameters of tomato seeds to determine the most effective concentrations. Then, we applied the chosen concentrations (2%, 5%, and 10%) of CTE as soil drench to tomato seedlings (Solanum lycopersicum L.) grown under salinity. Our findings revealed a decrease in the growth of tomato plants exposed to 50 mM of NaCl compared to unstressed ones. However, CTE supplementation, especially at 2%, to the stressed plants increased the plant height by 32.24% compared to stressed control without treatment and elevated biomass and chlorophyll content. Additionally, CTE decreased hydrogen peroxide and malondialdehyde accumulation and increased the activities of antioxidant enzymes: superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione S-transferase (GST). Moreover, CTE supplementation regulated the alterations in carbon and nitrogen metabolism by increasing the activity of carbon–nitrogen enzymes: phosphoenolpyruvate carboxylase (PEPC), malate dehydrogenase (NAD-MDH), glutamine synthase (GS), glutamate dehydrogenase (GDH), and aspartate aminotransferase (AAT). Furthermore, CTE application increased notably the content of indole acetic acid, soluble sugars, and amino acids and improved the expression of antioxidant metabolites like flavonoids and polyphenols. Overall, our investigations demonstrate that CTE can be used as biostimulant to enhance the salt stress tolerance of tomato plants.

In the North East of the Moroccan Mediterranean coast, 15 km south east of the Al Hoceima city, the coastal aquifer of Ghiss-Nekkour occupies an area of 100 km2. Its exploitation constitutes a priority economic imperative for the city of Al Hoceima and its hinterland, due to the tourist character of the city and the agricultural orientation of the region. In the surface of this study area, alternate rural-type habitats with autonomous sanitation systems, agricultural plots, uncultivated land, a few small industrial units, a local road network, in addition to the International Airport Charif El Idrissi. These are various potential sources of local anthropogenic groundwater contamination. Their intensity may grow with the socio-economic development that knows the region as a whole. In this work, the authors apply a new multicriteria approach of acronym “PRK Plus” to assess the sensitivity of the coastal aquifer Ghiss-Nekkour to anthropogenic pollution. The results obtained from this application show that despite the aggressiveness of the Ghiss-Nekkour groundwater pollution sources, 98% of the total surface area of the water table is “very little sensitive” to anthropogenic contamination.

In our study, we were interested in the reliability of large discrete systems. These studies can be based on Markov models or on Stochastic Petri Nets (SPNs) that are generally used for the analysis and synthesis of the models used in the different phases of a system's life. Markov models or SPNs are perfect for many cases, still, they suffer from the combinatorial explosion when analytically their state numbers increase as the complexity of the dynamic systems grows accordingly with their components. Such issue reflects itself in the slowness of these models to accomplish convergence. These different modelling tools make it possible to deduce the average behaviour and to obtain the performance indicators of the system studied, either by calculation or by estimation. We will present the Markov analysis of a system whose state space is finite as well as its estimator obtained using SPNs.

Fouling phenomenon is considered among the major reasons that cause significant increase of operating cost of desalination plants equipped with reverse osmosis (RO) membranes. This phenomenon is studied in the present work in the case of RO polyamide aromatic membranes using model seawater containing inorganic salts and colloidal compounds. Different solubility conditions of CaCO3and CaSO4were applied to study RO performances with and without colloid presence. During experiments, the membrane permeate fluxes were continuously monitored. Moreover, studies of chemical composition, structure, and morphology of the materials deposited on the membrane surface were conducted using energy dispersive microanalysis (EDS) X-ray diffraction and scanning electronic microscopy (SEM). Results show that in conditions of calcium carbonate oversaturation there is a reduction in the permeate flow of 11.2% due to fouling of the membrane by the precipitation of this compound. While in the same conditions of calcium sulphate oversaturation the reduction of the flow is 5%, so we can conclude that in conditions of oversaturation of both salts, calcium carbonate produces a greater fouling of the membrane that in its view causes greater decrease in the flow of permeate. All this based on the results of the test with both salts in oversaturated conditions. Resulting in the formation of calcite and gypsum crystals onto the membranes as XRD analyses stated. Additional presence of colloidal silica in those conditions intensifies strongly the fouling, leading until to 24.1% of permeate flux decrease.

In the North East of the Moroccan Mediterranean coast, 15 km south east of the Al Hoceima city, the coastal aquifer of Ghiss-Nekkour occupies an area of 100 km2. Its exploitation constitutes a priority economic imperative for the city of Al Hoceima and its hinterland, due to the tourist character of the city and the agricultural orientation of the region. In the surface of this study area, alternate rural-type habitats with autonomous sanitation systems, agricultural plots, uncultivated land, a few small industrial units, a local road network, in addition to the International Airport Charif El Idrissi. These are various potential sources of local anthropogenic groundwater contamination. Their intensity may grow with the socio-economic development that knows the region as a whole. In this work, the authors apply a new multicriteria approach of acronym “PRK Plus” to assess the sensitivity of the coastal aquifer Ghiss-Nekkour to anthropogenic pollution. The results obtained from this application show that despite the aggressiveness of the Ghiss-Nekkour groundwater pollution sources, 98% of the total surface area of the water table is “very little sensitive” to anthropogenic contamination.