Artificial neural network analysis of Moroccan solar potential

An artificial neural network (ANN) model is used to forecast the annual and monthly solar irradiation in Morocco. Solar irradiation data are taken from the new Satellite Application Facility on Climate Monitoring (CM-SAF)-PVGIS database. The database represents a total of 12 years of data from 1998 to 2010. In this paper, the data are inferred using an ANN algorithm to establish a forward/reverse correspondence between the longitude, latitude, elevation and solar irradiation. Specifically, for the ANN model, a three-layered, back-propagation standard ANN classifier is considered consisting of three layers: input, hidden and output layer. The learning set consists of the normalised longitude, latitude, elevation and the normalised mean annual and monthly solar irradiation of 41 Moroccan sites. The testing set consists of patterns just represented by the input component, while the output component is left unknown and its value results from the ANN algorithm for that specific input. The results are given in the form of the annual and monthly maps. They indicate that the method could be used by researchers or engineers to provide helpful information for decision makers in terms of sites selection, design and planning of new solar plants.     

Reduced reference image quality assessment based on statistics in empirical mode decomposition domain

This paper deals with the image quality assessment (IQA) task using a natural image statistics approach. A reduced reference (RRIQA) measure based on the bidimensional empirical mode decomposition is introduced. First, we decompose both, reference and distorted images, into intrinsic mode functions (IMF) and then we use the generalized Gaussian density (GGD) to model IMF coefficients of the reference image. Finally, we measure the impairment of a distorted image by fitting error between the IMF coefficients histogram of the distorted image and the estimated IMF coefficients distribution of the reference image, using the Kullback–Leibler divergence (KLD). Furthermore, to predict the quality, we propose a new support vector machine-based (SVM) classification approach as an alternative to logistic function-based regression. In order to validate the proposed measure, three benchmark datasets are involved in our experiments. Results demonstrate that the proposed metric compare favorably with alternative solutions for a wide range of degradation encountered in practical situations.     

An Effective Approach for the Development of Reliable YBCO Bulk Cryomagnets with High Trapped Field Performances

Widespread use of YBa₂Cu₃O_7‐δ (Y123) bulk superconductors as source of strong magnetic fields requires development of high‐performance materials sufficiently reliable with improved thermal transfer ability. An effective approach based primarily on the growth of bulk Y123 single domains comprising a holes‐network to diminish the oxygen diffusion paths is reported here, as well as their progressive annealing at high temperature under oxygen pressure to reduce undue stresses and processing time. Finely, it aims to stimulate the thermal exchange inside the superconductor and compensate for induced magnetic stresses during the field‐trapping process. The approach brings considerable time and energy savings, and turns out to knock down barriers having stymied hitherto the use of Y123 bulk superconductors for engineering applications. Indeed, it enables the achievement of a pore‐free and crack‐free microstructure yielding marked fracture toughness and promoting large size persistent current loops, thereby boosting the trapped field performances. The fostering of the internal thermal exchange leads the maximum trapped field B_max to shift to higher temperatures by up to 14 K. A value B_max of 6.34 T is attained at 17 K on ≈16 mm‐diameter reinforced pellet (disk area s = 1.99 cm²), resulting in an outstanding field density B_max/s=3.19 Tcm^?2.     

Vertical accuracy assessment of global digital elevation models and validation of gravity database heights in Niger

In this study, we assessed the vertical accuracy of ASTER GDEM (Advanced Space-borne Thermal Emission and Reflection Radiometer – Global Digital Elevation Model) version 2, AW3D30 (ALOS World 3D – 30m) and the 1 and 3 arc-seconds versions of SRTM (Shuttle Radar Topography Mission) in Niger Republic. We explored the GDEMs to evaluate large void and erroneous pixel areas. GDEMs were then compared to three kinds of ground control data located on several sites and all merged data after vertical datum matching. We also analysed the vertical accuracy by land cover and compared GDEMs to each other. We finally validated the gravity database heights by using the relatively most accurate GDEM. All GDEMs still contain void pixels except for SRTM3 CGIAR, it was then retained for the assessment with 1 arc-second GDEMs. The vertical accuracies in terms of RMS (Root Mean Square) and in m are: ASTER (6.2, 8.0, 9.8 and 9.2), AW3D30 (2.2, 2.1, 1.8 and 1.6), SRTM1 (3.8, 4.3, 2.5 and 2.9) and SRTM3 (3.7, 4.1, 2.4 and 2.7) compared to levelling data, local DEM of Imouraren, GPS (Global Positioning System) data and all merged data. Absolute height differences are less than 10 m at 74.00%, 99.99%, 99.91% and 99.98% for ASTER, AW3D30, SRTM1 and SRTM3, respectively. AW3D30 is the most accurate and ASTER is the least accurate. For all GDEMs, different accuracies were found depending on land cover classes that could be caused by the random spatial distribution of validation data. Small differences were observed between SRTM and AW3D30 and large values between the two models and ASTER similarly. The gravity database was validated using AW3D30, large values of height differences were found in the northern part in agreement with the database specifications and in the southern part indicating erroneous elevations.     

Simulation of PV-Wind-hybrid systems combined with hydrogen storage for rural electrification

Since many years, engineering, research and development of hybrid systems for rural electrification are strongly supported by computer simulations. Different software packages have been used according to the required level of details along with the progress of the project HYRESS. For the development of optimal system control and load/energy management strategy, different simulation models from APL (Alternative Power Library) have been used for a Hybrid PV-wind-hydrogen system that will be installed in the Essaouira region in Morocco. This library provides models developed by IWES for the simulation of regenerative power supply systems and it is used to investigate the integration of a hydrogen storage path in hybrid system operation.     

Aluminium clusters for molecular hydrogen storage and the corresponding alanes as fuel alternatives: A structural and energetic analysis

Bare and hydrogenated aluminium clusters Al_n (n = 5–7) are studied using density functional theory in order to evaluate the ability to store molecular hydrogen and to estimate the energy release upon combustion with the aim to understand these species as alternative fuel resources. Six sequential molecular hydrogenations are considered and are shown to occur without or very low activation barriers. The H₂ molecule uses its occupied σ orbital to react with an appropriate electron-deficient site of the cluster; this is generally followed by H migration leading to the favoured geometry. The combustion process produces alumina (Al₂O₃), water and a significant quantity of energy. The exothermicity seems to be largely independent of cluster size but it depends instead on the stored hydrogen quantity.     

Development of an experimental platform for research in energy and electrical machine control

This paper presents the development of a test bench dedicated for electrical machines and energy control, as realized by the research team of the Power Systems and Electrical Machines Laboratory (RME) of the National Institute of Applied Sciences and Technology (INSAT) in Tunisia. The principal components of the proposed test bench are explained, and the respective characteristics are given. This paper focuses on mounting low-cost sensors and developing reliable scientific results. The relevant obtained results in photovoltaic (PV) and wind energy fields, power measurement and control, as well as alternating current (AC) machine drives are likewise presented. These are supported by two signal processing controller boards based on Technosoft MCK240 and dSPACE DS1104 kits. In the wind energy field, some results relative to Self Excited Induction Generator dedicated to supplying isolated sites are discussed; in addition, water pumping is discussed for PV energy. In the AC drives area, the results of a closed loop control are presented using a developed direct voltage control (DVC) scheme implemented on dSPACE DS1104. Maps and interesting details of some realized sensors are also presented.     

High performance of bulk Mo2N and Co3Mo3N catalysts for hydrogen production from ammonia: Role of citric acid to Mo molar ratio in preparation of high surface area nitride catalysts

Hydrogen production from ammonia decomposition was studied using a series of unsupported high surface area molybdenum nitride (Mo₂N) and cobalt promoted molybdenum nitride (3%Co-Mo₂N) catalysts prepared with citric acid (CA) as a chelating agent. To elucidate the influence of citric acid amount in preparation conditions on the structure and catalytic activity, we prepared catalysts with different citric acid to Mo molar ratios i.e. CA/Mo = 1, 2, 3 and 4. The catalytic activity was evaluated in the temperature range of 300–600 °C at atmospheric pressure. The catalytic activity of the tested samples has changed in the following order of CA/Mo atomic ratio of 1 < 2 < 3 > 4. Therefore, the catalyst prepared by using CA/Mo ratio = 3 showed the highest catalytic activity. BET, XRD, XPS, SEM and TEM-EDS techniques were been used to characterize the catalysts. The increased activity of Mo₂N-3:1 and 3%Co-Mo₂N-3:1 catalysts was due to increased surface area, decreased particle size and increased relative proportions of Mo₂N and Co₃Mo₃N phases. The ammonia conversion for 3%Co-Mo₂N catalyst was increased from 75 to 97% at 550 °C with the increase of CA/Mo ratio from 1 to 3. This enrichment of activity in 3%Co-Mo₂N-3:1 catalyst is due to increased dispersion of Co₃Mo₃N microstructure on γ-Mo₂N platelets confirmed by SEM and TEM results. No deactivation was observed for any catalysts investigated in this study for ammonia decomposition.     

Analyse temporelle des lignes de transmission non uniformes avec effet de peau

This paper deals with a computational approach, based upon centered points finite-difference time-domain technique, for evaluating voltages and currents along nonuniform planar transmission lines terminated with arbitrary loads. To improve the accuracy of the method, the skin effect has been included into the algorithm by means of the approximation of the conductor internal impedance. Some configurations of nonuniform planar lines have been analyzed in order to show different aspects of the efficiency of this computational procedure.