Quantitative and qualitative characterization of the energy productivity of pilot digesters of animal manure

Youssef M'sadak, 

Résumé: In the optics of the control of the conditions of the fermentaire medium for a better energy valorization of biogas, this study proposes, like main aim, the follow-up and the evaluation on the one hand, of the quantitative productivity of the biogas produced on an experimental scale starting from avicolous droppings, and starting from bovine dejections, and on the other hand, of the gas qualitative productivity (gas composition and calorific value) on the level of the whole of digesters (experimental avicolous, rural bovine and industrial avicolous). Such a work made it possible to arise the principal observations hereafter: - The combined effect of the mode of food and the nature of the substrate on the quantitative energy performances of the experimental biogas product which is in favor of the digesters supplied uninterrupted with the avicolous droppings. - The performance of a digester from gas production point of view primarily depends on the nature of the matters to ferment, the agitation of the substrate, the temperature maintained during digestion and also of the adjustment of the pH and the DM introduced. - Rural or industrial biogas, undergoing a stage of post processing, present of better energy potentialities especially at the industrial scale in which the increase in the LCV can reach 25%. The qualitative energy performances of the rural digester are relatively limited compared to those of the industrial digester. This is with the least effectiveness of the systems of production and conditioning of the biogases employed by this last.

Mots clés: (Animal biomass; pilot digesters; gas quantitative productivity; gas composition; calorific value).

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Influence of the altitude in the diametric distribution of the Quercus suber in the Northwest of Tunisia.

Jdaidi Nouri, 

Résumé: Abstract The cork oak occupies a special place in the Mediterranean forest. In Tunisia, it is fairly represented in the Northwest (70000 ha), especially in the Ain Draham and Tabarka areas [3]. It is restricted to acid surrounding conditions with a mild climate and plays a very important ecological role, this way insuring the installation of a fairly diverse flora whole branched out enough floral and wildlife procession. It insures also a significant socio-economic role for the rural population which lived in this zone and adds to the national economy through the production and the export of cork. Going through a great made by people pressure, and a perfect worsening of the medium with the effect direct of the climatic change, the forests of oak cork are unable to grow again it naturally. So, and according to the variance analysis of the effect of height on the diametric structure of cork oak, one noted more than height decrease, more than the density of diameter's classes of cork oak is very significant and more there is chance to find young seedlings resulting from natural regeneration. These results show that the density of cork oak differs within the same height classes, this difference can be the result of the effect of factors environmental.

Mots clés: Keywords: Tunisia, cork oak, altitude, diameter classes.

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Distribution Generation Based on Fuel Cells, Drawbacks, Techniques and Solutions in Literature Review.

محسن عبد الله, 

Résumé: The energy crisis is one of the most critical phenomena happening in today’s world. The depletion of fossil fuels, the rise in oil prices, and the increase in power demand are the main causes of this problem. Concern over environmental conditions and human health make renewable energy one of the most viable alternative solutions to this crisis. Among various types of renewable energy, fuel cell technology shows a great potential in the electrical energy sector for several reasons, such as high efficiency, clean operation, and immunity to the adverse effects of weather conditions. Recent works prove that fuel cell technology is expected to be a better choice for distributed generation purposes. Distributed generation, which is installed near load centers, can moderate the stress of high electricity demand in the mainstream utility grid. This paper presents an overview of fuel cell technology, with emphasis on fuel cell types, characteristics, and applications. The differences among the various fuel cell types and the dynamic models of each type required for simulation are also discussed. Focus is given to the application of fuel cells in a distributed generation system, the requirements of a fuel cell-based generating system, and issues in distributed generation integration. The present study also discusses the power conditioning unit, which is an important component in the fuel cell-based generating system, as well as its control strategy. Discussion is likewise made on the use of suitable energy storage units for the fuel cell distributed generation system, with regard to battery types and storage control. By adding energy storage units to the fuel cell system, the capabilities of the existing generation system can improve system stability performance.

Mots clés: Fuel cell, energy storage system, power conditioning unit, distributed generation.

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Effet combiné de la température et de l'attaque au sulfate de magnésium sur la durabilité du mortier à base de ciment composé au laitier

Aziez Mohammed Nadjib, 

Résumé: Ce travail a pour but d’étudier l’effet de la température sur la durabilité des mortiers conservés dans un environnement riche en sulfate de magnésium (5% MgSO4). La résistance des mortiers après 12 mois d’immersion dans la solution sulfatique est évaluée par l’observation visuelle, la variation de la masse, la résistance à la compression, et l’analyse DRX. Aucun dégât n'a été observé dans les échantillons exposés aux sulfates à 20, 50 °C, sauf pour les mortiers exposés à 5 °C qui sont très sensible à formation de la thaumasite. Les résultats ont montré que l’augmentation de la température permet d’améliorer la résistance mécanique et n'accélère pas nécessairement la dégradation des mortiers en solution de sulfates de magnésium.

Mots clés: Durabilité, Température ; Attaque sulfatique, Sable, Thaumasite, Ettringite, Gypse, Mortier. ; Durabilité, Température ; Attaque sulfatique, Sable, Thaumasite, Ettringite, Gypse, Mortier. ; Durabilité ; Température ; Attaque sulfatique ; Sable ; Thaumasite ; Ettringite ; Gypse ; Mortier

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Study of planting densities effects on olive tree by using sap flow method

ابتسام كميشة, 

Résumé: Abstract: In the semi-arid and arid Tunisian climate where the olive tree is the dominant cropping specie the cultural practices adopted aimed primarily optimisation of the rainwater use. As part of the restructuring of the traditional olive tree grove, the revision of planting densities is envisaged. Thus, we conduct in 1988 an experimentation to test the revision of traditional planting densities by increasing the number of tree by ha according to the traditional density used. The densities tested vary from 51 to 156 trees by ha. From the 17th year of planting, despite the level of yields by hectare as elevated as the planting density is high, we have noticed a trend towards decline in the yield per tree for the denser parcel. Thus, we tried to analyze the functioning of the global tree water in connection with the planting density using state thermoelectric measuring of sap flow in order to quantify the water consumption and to clarify the influence of planting density on the water state of the tree. In addition, we have tried to identify the relationship between the seasonal dynamics the sap flow and its major determinants as the plant water conditions and the environment. These studies show the great capacities of the Chemlali olive-tree to be adapted to the hydrous conditions available. Indeed, we did not distinguish in a clear way of negative effects due to the highest densities, on the contrary for certain critical periods of the biological cycle of the tree these densities are distinguished by their best behavior, for example the spacing 10mx10m presents the highest values of clear photosynthesis by an average value of 17.46µmol.Co2.m-2.s-1 compared with 16.32µmol.CO2.m-2.s-1 for the spacing 14mx14m. This shows that this farming system exploited since 20 years can still be profitable. Other studies are necessary to better distinguish between the effect of the spacing and this while utilizing other biological and agronomic parameters.

Mots clés: Sap flow , f0 , fm, fv/fm, olive tree

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A New Robust Control for Doubly fed Induction Machine based on Type-2 Fuzzy Logic Controller

Saidi Abderazak ,  Naceri Farid , 

Received date: 01-01-2019    Publication date: 28-02-2019    pages  845-857.   

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Ascaridiose du cheval dans la région de Tiaret : fréquences et proposition de moyens de contrôle

Kouidri Mokhtaria ,  Selles Sidi Mohammed Ammar ,  Affane Zohra ,  Mechkour Lilia ,  Meddah Khaldia Khaldia ,  Khellil Schahrazed Djihane ,  Haddouche Zohra , 

Date de réception: 18-02-2019    Date de publication: 28-02-2019    pages  858-864.   

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Chemical and Physical Investigations on the barite of Ain Mimoun ore deposit –Khenchela - North-eastern Algeria

Abdellaoui Khedidja , 

Received date: 09-10-2018    Publication date: 28-02-2019    pages  865-877.   

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Compilation d’un nouveau logiciel pour l’identification des espèces d’insectes orthoptères

Hadj Seyd Abdelkader , 

Date de réception: 25-02-2019    Date de publication: 28-02-2019    pages  878-887.   

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Contamination fongique des amandes commercialisées dans les marchés de trois villes algériennes: Blida, Médéa et Tipaza

Matmoura Amina ,  Bouti Karima ,  Bouras Noureddine ,  Houmani Zahia , 

Date de réception: 12-02-2019    Date de publication: 28-02-2019    pages  888-896.   

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Effect of internal erosion (suffusion) on dikes stability: Finite element analysis

Bouziane Abderrezak , 

Received date: 02-06-2018    Publication date: 28-02-2019    pages  897-907.   

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Forced convection heat transfer of power-law fluids around a confined obstacle cylinders

Laidoudi Houssem , 

Received date: 21-05-2017    Publication date: 28-02-2019    pages  908-923.   

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Low power adaptive Motion Estimator for real time applications H.264/AVC Codec

Salah Dhahri ,  Abdelkrim Zitouni , 

Received date: 29-10-2018    Publication date: 28-02-2019    pages  924-930.   

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Physical Properties of Semiconductors Used For Renewable Energies

Bouhfs Choayb ,  Chitroub Mohamed , 

Received date: 23-01-2019    Publication date: 28-02-2019    pages  931-936.   

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Santé mammaire et baisse laitière quantitative conséquente aux comptages cellulaires individuels élevés et à partir des scores linéaires correspondants chez deux grands élevages bovins (Sahel Tunisien)

M'sadak Youssef , 

Date de réception: 10-07-2018    Date de publication: 28-02-2019    pages  937-948.   

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Tabu Search & Gpu-Based Genetic Algorithm to Solve The Job Shop Scheduling Problem With Blocking

Aitzai Abdelhakim ,  Dabah Adel ,  Boudhar Mourad , 

Received date: 23-12-2018    Publication date: 28-02-2019    pages  949-961.   

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The effect of the direct self curling polymerization on the thermal and structural properties of the Polyaniline doped by unsaturated carboxylic acid

Naar Nacira , 

Received date: 23-11-2017    Publication date: 28-02-2019    pages  962-970.   

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Thermal study of photo-polymerization reaction in the preparation of composite materials based on polymer

Hadjou Bélaid Zakia ,  Benkhaled Fatima Zohra ,  Beroguiaa Derouiche , 

Received date: 02-06-2018    Publication date: 28-02-2019    pages  971-977.   

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