Nutrients Deficit and Water Stress in Plants: New Concept Solutions Using Olive Solid Waste

Great efforts were deployed by researchers to mobilize water resources while is becoming rarer and to control with efficiency the water besides nutrient needs for the plant. Autonomous water and nutritional anti-stress device for plants (AWANASD) based on the recovery of rainwater patented by Medhioub et al. fits into this general framework. Scientific efforts were also dedicated to preserve the environment and minimize energy consumption through using agricultural waste materials in different fields. This chapter provides a new concept based on the use of the olive solid waste in AWANASD as water storage and nutrient elements for plants giving rise to the new system called AWANASD-OSW

Physico-Chemical Study of Coating Formulation Based on Natural Apatite for the Elaboration of Microfiltration Membrane

This work deals with the experimental characterization of the rheological properties of a dip solution which will be used to elaborate a new apatite/clay microfiltration membrane by deposition using slip casting process of the active layer on a tubular support based on natural clay previously prepared. So, the rheological study of various coatings with different concentration of apatite powder, polyvinyl alcohol (PVA) and water under different conditions regarding temperature and stirring time was done. It was found that the suitable suspension should follow a rheo- thickner behavior having a viscosity in the range of 30-35 mPa s at room temperature of 25 to 30°C. The optimum conditions then found to achieve these properties were: a suspension of 4% of apatite, 40% of PVA stirred for 180minutes. The study reveals also that the thickness of the active membrane layer depends on the coating time

Effect of heating–cooling cycles on transient creep strain of high performance, high strength and ordinary concrete under service and accidental conditions

International audienceno abstrac

Étude du comportement du béton à hautes températures (une nouvelle approche thermo-hydro-mécanique couplée pour la modélisation du fluage thermique transitoire)

La connaissance du comportement du béton soumis à de hautes températures constitue un enjeu de grand intérêt pour les applications du génie nucléaire et pour l évaluation de la sécurité dans des constructions de génie civil. En outre, les incendies récents dans les tunnels européens (sous la Manche, Le Mont-Blanc, Great Belt Link, Tauern), ayant entraîné des dommages aux structures en béton ainsi que des pertes humaines et économiques très importantes, ont suscité un nouvel intérêt pour l évaluation de la performance du béton dans les conditions accidentelles. En effet, les hautes températures entraînent une dégradation des propriétés mécaniques (rigidité, résistance ) du fait de processus de fissuration générés par l effet simultané des efforts appliqués, de la température et de pressions de pores. Tous ces processus nécessitent une modélisation couplée des phénomènes physico-chimiques dont le matériau est le siège ainsi que leurs interactions avec les propriétés de transport de masses, de transfert de chaleur et du comportement mécanique. En outre, quand le béton est soumis à l action combinée du chargement et de hautes températures, sa déformation se décompose, conventionnellement, en deux classes de composantes additives. On distingue : - des déformations thermo-hydriques libres incluant l expansion thermique et le retrait du béton. Le retrait est essentiellement dû à la dessiccation du matériau et à sa déshydratation. - des déformations thermiques sous charge qui consistent en une composante élastique dépendante de la température, une déformation de fissuration et une composante de fluage thermique transitoire. Cette dernière est généralement liée au fait que les transformations physico-chimiques, comme la déshydratation et la dessiccation, se produisent sous charge, ce qui induit un réarrangement de la microstructure du béton et donne lieu à cette déformation macroscopique. Dans ce travail de thèse, une nouvelle approche pour la modélisation de la composante transitoire de la déformation thermique induite sous charge est proposée afin de prédire le comportement du béton à hautes températures. Dans cette approche, le fluage thermique transitoire est décomposé en fluage de dessiccation et en une composante, nouvellement introduite, de fluage de déshydratation. La première composante est due à l évolution de l hygrométrie du matériau tandis que la deuxième est due à sa déshydratation du fait de l augmentation de la température. Par conséquent, une variable de déshydratation est définie et est introduite comme une variable régissant le fluage thermique transitoire lorsque la température dépasse la valeur seuil de 105C. Ce modèle thermo hydro endommageable est implémenté dans un code aux éléments finis. Des simulations numériques sont effectuées et comparées à des résultats expérimentaux pour analyser les capacités prédictives du modèle proposéThe knowledge of concrete structures under high temperatures is of great interest in nuclear engineering applications and in safety evaluation against fire in civil constructions. Furthermore, increasing recurrence of tunnel fires in Europe (Channel, Mont-Blanc, Great Belt Link, Tauern) resulting in damage of concrete causing heavy economical and human losses, have leaded to a renewed interest in the behaviour of concrete at accidental conditions of temperature. In fact, when concrete is exposed to high temperatures, this leads to an evaporation of the free water, a pore pressure built up and a heat and mass transfer into the concrete structure which cause an incompatibility between the expanding aggregates and the shrinkage cement past. This incompatibility leads to the material degradation and microcracking. These entire phenomena will influence the thermal, hygral and mechanical material proprieties of the concrete. Therefore, the need to design durable concrete structures requires a robust modeling of all the processes involved in the deformation and degradation mechanisms of the material and it becomes essential to consider their coupling. When concrete is under the effect of combined mechanical loads and high temperature distributions, it exhibits strains which are conventionally split to a set of additive components: Stress-free components, referred to thermo-hygral strains, which include thermal expansion and hygral shrinkage due to both drying and dehydration. Stress induced thermal strains which mainly consist in a temperature dependent elastic strain, a micro-cracking strain and an additional component, commonly referred to as transient creep. This additional component is generally related to the fact that physical transformations, such as drying and dehydration, are occurring under sustained stress fields, which lead to a rearrangement of the evolutionary microstructure and give rise to this macroscopically measured strain. In this study, a new approach for modeling the transient component of the induced thermal deformation under load is proposed in order to predict the concrete behavior when subjected to high temperatures with a concomitant applied load. This component is conventionally referred to as transient creep strain. In this approach, the transient creep strain is split in to a drying creep component and a newly introduced dehydration creep strain. The former is related to the evolution of the hygrometric state of the material, while the later is related to the material dehydration which results from the heating induced chemical transformations. Therefore, a dehydration variable is defined and then introduced as a driving variable of the transient creep for temperatures exceeding 105 C. This thermo-hydro-damage model is implemented using a finite element code and numerical simulation are performed and compared to experimental results in order to assess the predictive ability of the proposed modelPARIS-EST Marne-la-Vallee-BU (774682101) / SudocSudocFranceF

The effect of ageing and heat treatment on microstructure evolution of a commercial cement paste

This paper reports the microstructural changes on a 2 year-old cement paste, unprotected from contact with air, heated to various temperature regimes up to 1000 °C in steps of 100 °C for a constant period of 6h. This work has been carried out using a thermal analysis technique and XRD. The parameter involved in this study is the state of the samples: powdered samples and blocks of paste. As a result, it is possible to monitor the major features of the experiments, i.e. the phase's existence domains and their growing of hydrated calcium silicate, portlandite, calcite as well as their decaying: alite, belite and lime. The result shows higher amounts of portlandite and carbonate calcium for the aged cement paste compared to fresh OPC. The carbonation is more marked for the blocks of paste while the crystallinity degree is higher for the powdered cement paste samples. The new portlandite formed during cooling continues to exist until the 1000 °C temperature plateau. Nevertheless, this portlandite is less crystalline than the original one, and its temperature of thermal decomposition gets lower. An increase in the total weight loss and in the crystallinity at 900 and 1000 °C, compared to 800 °C is also noted. The CSH dehydration to ²-C2S and C3S become significant above 600 °C and the corresponding rate increases with increasing temperature

Thermal stability and microstructural changes in 5 years aged cement paste subjected to high temperature plateaus up to 1000°C as studied by thermal analysis and X-Ray Diffraction

This paper studies the thermal effects on the mineralogical properties as well as the microstructure of 5 year-aged cement pastes, unprotected from contact with the air, heated up to various temperature up to 1000 °C in steps of 100 °C for a constant period of 6 h by studying the TGA/DTG and XRD curves. In order to simulate a real situation of a fire, in this research, the state of the specimens is in a block and the cooling regime is an air-cooling regime. The results show that ageing of the cement paste induces higher carbonation of the cement paste and higher uptake of humidity. The new portlandite formed during cooling and the decarbonation reaction continue to exist up to 1000 °C and 800 °C temperature plateaus, respectively. XRD tests show the presence of the C-S-H gel for all temperature plateaus and the coexistence with its products ²-C2S and C3S beyond the 500 °C temperature plateau. In order to proof the effect of ageing, the state of samples and the impact of the cooling regime in the thermal stability and in the microstructure of the cement paste after being subjected to high temperatures, a comparison has been made between the results of powdered cement paste aged for 2 years and cooled in air and the results of blocks of cement paste, also aged for 2 years, but cooled at the desiccator

Elaboration de membranes de microfiltration et d'ultrafiltration en céramique à base d'argile tunisienne

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Multi-agent preemptive longest queue first system to manage the crossing of emergency vehicles at interrupted intersections

Abstract Favouring the crossing of Emergency Vehicles (EVs) through intersections in urban cities is very critical for people lives. There have been several efforts toward developing Traffic Signal Control Systems (TSCS) dedicated to control efficiently the traffic flow, but few are the efforts toward developing Traffic Signal Priority Systems (TSPS) dedicated to favour the crossing of EVs (such as ambulances, firefighters, police cars, etc.). Multi-Agent Systems were considered to develop several distributed TSCS, while very few works have developed distributed TSPS. Such systems lack on dealing with the EVs crossing issues while maintaining a fluid state of the traffic. In the literature, the Longest Queue First – Maximal Weight Matching (LQF-MWM) is proved to guarantee a stable TSCS. Recently, the LQF-MWM technique is increasingly used to benchmarck and assess adaptive TSCS. Moreover, the preemption is one of the most effective techniques used to prioritise the crossing of EVs. This paper is the first to rely on LQF-MWM assumptions, preemption technique, and Multi-Agent Systems to design a distributed TSPS. The suggested system has two main purposes, which are the guidance of EVs and the control of traffic signals. Nine agents are implemented to govern a network of nine intersections, where each agent uses the Multi Agent System based Preemptive Longest Queue First – Maximal Weight Matching. We have referred to VISSIM traffic simulation software for benchmarking and analysis. To assess the suggested system, we have developed a distributed and preemptive version of VISSIM Optimized Stage-Based Fixed-Time algorithm. Python is considered to develop the suggested systems, and Spade platform is considered as agents’ platform. Several Key Performance Indicators are considered to assess the performance of all controllers including delay time, travel time, vehicles queue occupancy, number of stops, distance traversed, and speed. Experimental results show a competitive performance of the developed system to maintain a fluid traffic and guide efficiency EVs

Phase assemblage of a 5 year-old cement paste after submission to various high temperature and cooling regime.

In case of fire in a structure, concrete undergoes internal transformations that can alter its durability. It is also important to take into account the effect of the cooling regime after temperature exposure on the phase assemblage of the cementitious matrix. An experimental investigation was carried out to investigate the changes of a cement paste, heated up to various temperature up to 1000°C then cooled in water or cooled in air for comparison. Quantitative evolution of phase assemblage is obtained by various techniques (TGA, XRD, NMR and ICP-AES). For both cooling regimes, the hydrated crystallised phases tend to become disordered phases for lower exposition temperature. These phases coexist with anhydrous products for intermediate temperature and these new anhydrous phases become the majority for higher temperature. However, the two cooling regimes show differences. Equilibrium of hydrated aluminate phases is modified, (e.g. AFm/AFt ratio). There are structural modifications of the phases in particular for C-S-H. For water cooling regime, beyond 600°C, a leaching is observed in particular for calcium