Ensuring (QoS) in wireless sensor networks (WSNs) is a challenging issue due to the lack of resources and energy exhausting of sensor nodes. In this paper we propose a new QoS aware routing protocol for multi-hop wireless sensor networks based on cross-layer interaction between the network, MAC and physical layers. At physical layer, a link quality estimator is studied for the purpose of evaluating link quality. At MAC layer, a differentiated services mechanism is used to distinguish between real time and non-real time packets and to allocate more channel resources for real time traffic; TDMA slots also have been modified to allocate more and earlier slots to real time packets. At network layer, a routing path selection algorithm is introduced for QoS optimisation. Simulation results show that our proposed protocol improves network’s performances in terms of energy efficiency and QoS.
Et si Jules Vallès (1832-1885), Louis-Ferdinand Céline (1894-1961) et Alain Soral (1958-...) partageaient un même profil psychologique et sociologique. C'est ce que cette thèse a tenté de prouver en établissant les conditions de production de l'écrivain moderne engagé auprès du peuple.
Copper destined for electrical cabling require a compromise of mechanical properties and electrical resistivity. The drawing process accompanied by the formation of crystalline defects, such as gaps and dislocations, which leads to the increase in hardness, and therefore to the increase in resistivity, a very important characteristic for the conductivity and the efficiency of the cable. The scope of this work is to investigate the phenomenon of deformation texture evolution while copper wire drawn destined for electric cable-making and to understand its relationship with the electrical conductivity. In this study, we notice that the hardness and the resistivity increase with an increase of the deformation level. On the other hand, a slight decrease in the resistivity of the wires was observed after a holding time of 30 min at 260°C. The annealing of wires at 260°C for 9 min of holding time leads to a recrystallisation especially for high deformations and a gradual return of the mechanical properties and of the microstructure towards a state close to the state of the wire rod with the extension of time . The recrystallization texture is composed of the same components as the drawing texture, fibers <111>//ND (Normal Direction) and <001>//ND. The decrease in the intensity of the fiber after annealing is observed. On the other hand, the fiber <001> // ND remains stable.
The performance of photovoltaic (PV) module is affected by outdoor conditions. Outdoor testing consists installing a module, and collecting electrical performance data and climatic data over a certain period of time. It can also include the study of long-term performance under real work conditions. Tests are operated in URAER located in desert region of Ghardaïa (Algeria) characterized by high irradiation and temperature levels. The degradation of PV module with temperature and time exposure to sunlight contributes significantly to the final output from the module, as the output reduces each year. This paper presents a comparative study of different methods to evaluate the degradation of PV module after a long term exposure of more than 12 years in desert region and calculates uncertainties in measuring. Firstly, this evaluation uses three methods: Visual inspection, data given by Solmetric PVA-600 Analyzer translated at Standard Test Condition (STC) and based on the investigation results of the translation equations as ICE 60891. Secondly, the degradation rates calculated for all methods. Finally, a comparison between a degradation rates given by Solmetric PVA-600 analyzer, calculated by simulation model and calculated by two methods (ICE 60891 procedures 1, 2). We achieved a detailed uncertainty study in order to improve the procedure and measurement instrument.
Un cuiseur solaire boîte à surface réceptrice inclinée (CSBSRI) a été développé et testé à l’Unité de Recherche Appliquée en Énergies Renouvelables, sous les conditions climatiques de Ghardaïa, Algérie. Les performances thermiques du cuiseur sont analysées selon la procédure internationale de Mullick en termes de deux paramètres (F1, F2), le temps d’ébullition est calculé et la courbe caractéristique de notre cuiseur est également déterminée. En outre, les valeurs de puissance de cuisson sont calculées à partir des tests expérimentaux réalisés suivant le standard international de Funk et représentées en fonction de la différence de température entre l’eau et l’ambiance. Le cuiseur solaire réalisé, permettant une bonne interception des rayons solaires démontre de meilleures performances thermiques comparées à d'autres cuiseurs boîtes existants. (A box type solar cooker with inclined intercept area (BSCSRI) was designed and tested at Applied Research Unit on Renewable Energies under Ghardaîa (Algeria) prevailing weather conditions. The thermal performances of the cooker was analyzed using Mullick international procedure in term of two figures of merit, the characteristic boiling times was also calculated and the characteristic curve of the cooker was determinated. Furthermore, experiments also considered the requirements for the Funk’s international standard test procedure for calculating the cooking power and was correlated with the temperature difference between the cooking fluid and the ambient air. The realized cooker, which allows much higher solar radiation interception, has good thermal performances compared with others cookers found in the literature.)
Un cuiseur solaire boîte à surface réceptrice inclinée (CSBSRI) a été développé et testé à l’Unité de Recherche Appliquée en Énergies Renouvelables, sous les conditions climatiques de Ghardaïa, Algérie. Les performances thermiques du cuiseur sont analysées selon la procédure internationale de Mullick en termes de deux paramètres (F1, F2), le temps d’ébullition est calculé et la courbe caractéristique de notre cuiseur est également déterminée. En outre, les valeurs de puissance de cuisson sont calculées à partir des tests expérimentaux réalisés suivant le standard international de Funk et représentées en fonction de la différence de température entre l’eau et l’ambiance. Le cuiseur solaire réalisé, permettant une bonne interception des rayons solaires démontre de meilleures performances thermiques comparées à d'autres cuiseurs boîtes existants.
