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Yahia M.,University of Limoges | Tao J.W.,National School of Hydraulic Engineering, Blida | Sakli H.,National Engineering School of Tunis
Progress In Electromagnetics Research C | Year: 2013

We hybridize vector Finite Element Method (FEM) and a Modified Multimodal Variational Formulation (MMVF) to the accurate and fast design of complex isotropic rectangular filters. The MMVF is applied to the full-wave description in the rectangular waveguides while the FEM characterizes waves in the arbitrarily shaped discontinuities. The proposed hybrid method is applied to the full-wave analysis of circuits with great practical interest (i.e., cross-shaped iris and multimode filters), thus improving CPU time and memory storage against several full-wave FEM based Computer Aided Design (CAD) tools (i.e., HFSS High Frequency Structural Simulator). The performances of the proposed hybrid method are validated with experimental results and HFSS simulations.

Ladoux P.,National School of Hydraulic Engineering, Blida | Raimondo G.,Airbus | Caron H.,French National Railways Company SNCF | Marino P.,The Second University of Naples
IEEE Transactions on Power Electronics | Year: 2013

This paper presents a new technique in voltage balancing for single-phase railway substations. Using the concept of chopper-controlled impedance, the authors study the feasibility of an active Steinmetz circuit based on ac choppers. The low power losses in semiconductor devices make the proposed topology an interesting alternative to classical solutions such as those based on voltage source inverters. Design criteria are presented using information obtained from measurements carried out on a substation of the French National Railways. Finally, the study is validated by means of simulations and experimental results carried out on a 1.5 kVA prototype. © 2013 IEEE.

Mehaiguene M.,National School of Hydraulic Engineering, Blida | Meddi M.,National School of Hydraulic Engineering, Blida | Longobardi A.,University of Salerno | Toumi S.,National School of Hydraulic Engineering, Blida
Journal of Arid Environments | Year: 2012

Low flow hydrological regimes are crucial for an efficient development of water resources management tools, especially in those areas stressed by the combination of a dry climate and an excessive water demand, such as the Mediterranean basins. A lot of effort has been made by the worldwide scientific community toward the prediction of low flows features in ungauged catchments. The aims of the present study are: (1) the quantification of low flows characteristics, in particular with regard to the BFI and (2) the application of a simple regional approach to predict the BFI at ungauged sites. The investigated area is located in North West Algeria and has an extension of about 130,000 km 2. The relevant extension and the poorly dense monitoring network, which consist in 24 hydrometric stations, require the identification of homogeneous regions, for further application of simple linear regional regression models. Regions delineation is accomplished through the Principal Component Analysis method (PCA) and the cluster analysis, based on physiographic and climatic data. Three significantly different homogeneous areas have been identified, and comparisons between global and local regional multiple linear regression models indicate a large percentage of BFI explained variance in each area. © 2012 Elsevier Ltd.

Ayad A.,CNRS Study of Microstructures, Mechanics and Material Sciences lab | Ayad A.,National School of Hydraulic Engineering, Blida | Ayad A.,University of Mentouri Constantine | Wagner F.,CNRS Study of Microstructures, Mechanics and Material Sciences lab | And 2 more authors.
Computational Materials Science | Year: 2013

A modification of the Potts model for grain growth is presented. We add to the site energy a grain size factor that favors growth of large grains and whose magnitude has been optimized with respect to various aspects. The motivation for such a modification as well as the consequences in term of calculation speed are presented. The capabilities of this modified model are checked by comparing several characteristics of the microstructures obtained after various grain growth simulations with experimental data obtained for an IF steel. One large EBSD map, made at the end of the primary recrystallization, is used directly as the initial image for the calculations. A second EBSD map, obtained after grain growth (with a mean diameter of the grains about twice the initial value) was used for comparisons between the simulations and the experiment. The grain size distribution, the grain boundary character distribution and the crystallographic texture are reproduced rather well with this modified model using a moderate grain size factor effect. Also the speedup of the calculation is quite significant. © 2012 Elsevier B.V. All rights reserved.

Abbes A.S.B.,University of Science and Technology of Oran | Meddi M.,National School of Hydraulic Engineering, Blida
International Journal of Hydrology Science and Technology | Year: 2016

The watershed of the studied region, part of the large basin of Macta situated in the north-west of Algeria, is submitted to flash floods and is particularly dangerous. Facing to the recurring of those catastrophic events, the understanding of hydrologic process constitutes a strategic axis of prevention against floods. Functioning indicators of the basin have been searched for by modelling of the flow on different floods observed at level of the stations established along Mekkera Wadi. Among hydrologic models, the Muskingum model has been chosen for floods propagation study and estimations of flows, and the QdF model is used to evaluate the extreme quintiles and build the hydrographs of different return periods. The floods episodes observed at level of stations of Sidi Ali Benyoub and of Sidi Bel Abbès are characterised by importance of damages caused. The town of Sidi Bel Abbès built in the major bed of Mekkera and so the communes situated in the plains are the most exposed to these sudden floods. Copyright © 2016 Inderscience Enterprises Ltd.

Toumi S.,National School of Hydraulic Engineering, Blida | Meddi M.,LGEE | Mahe G.,IRD | Mahe G.,Montpellier University | Brou Y.T.,University of Artois
Hydrological Sciences Journal | Year: 2013

In this study, remote sensing and geographic information systems (GIS) are implemented in order to map and assess water erosion using the Universal Soil Loss Equation (USLE) in the Wadi Mina watershed in Algeria. The study area is characterized by great irregularity in rainfall which is mainly generated during storm events. The region is also known for its steep slopes, marly lithology and very sparse vegetation cover, making it more exposed and vulnerable to erosion. The USLE model can be described as the combination of six factors that feature the specific characteristics of the watershed. Data from multi-temporal remote sensing analysis and GIS are used to individually assess and map each factor. Integration of thematic maps for the USLE factors in the GIS is used to identify the impact of each factor on soil loss, as well as to rank the relative importance of the erosion zones, and further to quantify soil loss in the investigated region. © 2013 © IAHS Press.

Meddi M.M.,National School of Hydraulic Engineering, Blida | Assani A.A.,University of Quebec at Trois - Rivieres | Meddi H.,National School of Hydraulic Engineering, Blida
Water Resources Management | Year: 2010

We analyzed the temporal variability of annual precipitation measured at five stations in the Macta (14,380 km2) and Tafna (4,949 km2) catchments located in northwestern Algeria, in connection with climate indices over the 1950-2004 period. Analysis of the temporal variability using linear regression and Pettitt test revealed a significant decline in annual rainfall in the mid-1970s in both basins. Furthermore, a decrease of at least 20% of total annual rainfall is also observed at all five stations. As for the relationship between climate indices and variability of annual precipitation, canonical correlation analysis shows that, from 1950 to 2004, precipitation at the five stations are negatively correlated with NINO4 and, to a lesser degree, with NAO. © 2010 Springer Science+Business Media B.V.

Hallouz F.,National School of Hydraulic Engineering, Blida | Meddi M.,National School of Hydraulic Engineering, Blida | Mahe G.,Mohammed V University
Revue des Sciences de l'Eau | Year: 2013

A change in rainfall will likely cause a change in the availability of water resources, and impacts on the human population should be important. Water resources are also subject to anthropogenic pressure that continues to grow: change of land use, dam construction, and groundwater withdrawals. The catchment basin of Wadi Mina, around 6,000 km2, located in northwest Algeria and tributary of the Wadi Cheliff, experiences a significant spatial and temporal variability of rainfall and discharges. The regionalization of the annual rainfall for this basin was conducted using data from 26 rainfall stations with 77 years of observations (1930-2007). Using statistical tests for detecting breaks in time series, we showed a decrease of 19-20% in annual rainfall over the Wadi Mina basin, mostly around 1976, and a break in time series of monthly and annual discharges at five gauging stations, starting in the mid-1970s and continuing until the 1980s. Over the whole studied discharge time series, we detected a decrease for all months, but it is mainly during the months of February, March and April, i.e., the end of the humid season, that they are the most significant. During recent years, no trend has been observed. At this scale, rainfall actually decreases significantly and steeply since 1960. Climate change currently affecting the Mediterranean is likely to have important consequences on the hydrological regimes of coastal rivers.

The constant growth of our need for water requires mobilization of surface water. The construction of dams can be envisaged, but many of them are threatened by early sedimentation; there is clearly a need for tools to quantify and forecast sediment deposition. Reservoir sedimentation can be simulated for different operating periods and understanding the process of sediment transport and deposition is a focus of many approaches: prediction, stochastic modeling, mathematical models and physical models have been used. Multiple interactions exist among bed load sediment, sediment transported near the river bed surface, and suspended sediment, resulting in different modes of transport. This contribution presents a numerical model that allows the simulation of the morphologic behaviour of river bed. The stages of its development are described in detail and the resulting computer code is then applied to a validation site. A section of 17 km is studied, between a dam in service and a hydrometric station located upstream of the dam. Sediment transport in the natural stream is presented by a system of one-dimensional equations describing a water-sediment mixture and translating the laws of conservation. The numerical method used is a finite difference method using an implicit scheme. It is first-order in time and second-order in space. Equations for free surface flow, for unsteady and gradually varied conditions, are used. Combined with the sediment continuity equation, these equations form the Saint-Venant-Exner model. The obtained results show the contribution of bed load transport in the sedimentation of the reservoir in a semi-arid zone.

Meddi M.,National School of Hydraulic Engineering, Blida
Journal of Urban and Environmental Engineering | Year: 2013

Soil erosion by rain and surface runoff is an important problem in the Mediterranean countries. The study of the relationship between erosion and sediment transport with hydrological and climatic factors have been conducted in many countries around the world. The aim of this work is to show rainfall impact on the variability of spatial and temporal concentration in twelve drainage basins in the west of Algeria. We will also seek to find a representative parameter of rainfall erosive potential on a Time and spatial scale. When studying sediment transport in twelve drainage basins of the Centre and the west of Algeria, we have found that the modified Fournier index Which explains much of the specific degradation compared to the Fournier index. The study of the temporal variability of the annual rainfall series, modified Fournier index and concentration of the precipitation in the year for a series from 1930 to 2007 showed a negative trend of the two variables. The annual rainfall and modified Fournier index have declined by more than 20%. This decline is more significant in inland areas. © 2013 Journal of Urban and Environmental Engineering (JUEE). All rights reserved.

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