Entity

Time filter

Source Type


Vinson D.S.,Duke University | Tagma T.,University Ibn Zohr | Tagma T.,Hassan 1st University of Settat | Bouchaou L.,University Ibn Zohr | And 4 more authors.
Applied Geochemistry | Year: 2013

Salinization in groundwater systems can induce water-rock interaction, including the release of naturally-occurring trace elements of health significance such as radium (Ra), with possible implications for the usability of water resources in addition to the increase of dissolved solids (TDS) concentrations. In general, radium mobility is limited by chemical removal mechanisms including adsorption onto clays and/or Mn and Fe oxides, exchange processes, and coprecipitation with secondary barite. In order to examine the effect of aquifer salinity gradients on the distribution of naturally-occurring Ra in fresh to saline groundwater and the relationship to water-rock interaction and Ra removal mechanisms, two contrasting systems were investigated: the shallow unconfined coastal aquifer in Agadir (southwestern Morocco) and the confined Cretaceous (Cape Fear) and Pliocene (Yorktown) aquifers of the Atlantic Coastal Plain (North Carolina, USA). Geochemical and isotopic indicators of salinity sources (e.g. cation ratios, δ18O, δ2H, Br-/Cl-, δ34S-SO42-,δ18O-SO42-) were used to identify the relative contributions of seawater and other saline waters and subsequent geochemical modification by water-rock interaction. Radium activities (224Ra, 226Ra, 228Ra), radon-222, alkaline earth metal (Mg, Ca, Sr, Ba) concentrations and ratios, and 87Sr/86Sr ratios were analyzed to identify water-rock interaction processes affecting alkaline earth metals including Ra. The Morocco coastal aquifer is generally oxic, exhibits a range of salinity and water types (Cl- 163-2120mg/L, median 932mg/L), and exhibits Ca/Na ratios above the seawater value, typical of monovalent-divalent cation exchange (base-exchange reactions) in coastal aquifers. In contrast, the Atlantic Coastal Plain aquifers are anoxic, sulfate-reducing, cover a wider salinity range (Cl- 5-9890mg/L, median 800mg/L) representing a transition between Na-HCO3- and Na-Cl- waters, and exhibit Ca/Na ratios below that of modern seawater typical of reverse base-exchange reactions. Possible salinity sources in the Morocco coastal aquifer include seawater intrusion, Mesozoic evaporites, other natural saline waters, and/or wastewater, whereas the Atlantic Coastal Plain is primarily affected by old seawater present in the aquifer system. Radium activities are generally low and vary significantly within each aquifer, for example 226Ra ranges from 1.8-27.7mBq/L in the Morocco coastal aquifer (median 8.1mBq/L) and 1.9-214mBq/L in the Atlantic Coastal Plain (median 18.9mBq/L). The highest Ra activities were observed in the most saline wells sampled in the Atlantic Coastal Plain. At total dissolved solids (TDS) concentrations above an apparent threshold of ~5000mg/L, radium activities increase in a generally linear fashion with salinity in the Atlantic Coastal Plain, broadly comparable to previous studies indicating a threshold range of ~3000-10,000mg/L. At lower TDS concentrations, water-rock interaction processes that vary with local aquifer conditions appear to control Ra distribution rather than merely salinity. In the Morocco coastal aquifer, adsorption of Ra and coprecipitation with secondary barite are apparently favorable to control Ra levels in groundwater. Radium removal in the anoxic Atlantic Coastal Plain aquifers appears to be associated with adsorption and/or exchange processes, with the additional possibility of barite precipitation in the Cape Fear aquifer indicated by barite saturation. Overall, the locally-variable factors that can control Ra sources and mobility in fresh to brackish groundwater at near-neutral pH include variation in solid-phase radioactivity, redox state affecting adsorption sites, availability of competing divalent cations, and barite saturation. © 2013 Elsevier Ltd. Source


Sardi A.,Hassan 1st University of Settat | Zbitou J.,Hassan 1st University of Settat | Errkik A.,Hassan 1st University of Settat | El abdelaoui L.,Hassan 1st University of Settat | And 3 more authors.
International Journal of Microwave and Optical Technology | Year: 2016

In this paper, a novel design of microstrip branch line Coupler (BLC) is designed and simulated by using FR4 substrate at the operating frequency 3.55 GHz worldwide interoperability for microwave access (WiMAX), the proposed coupler is designed by using open stubs Technique. After a theoretical study on the use of open stubs, we present the simulation results of this coupler by using ADS from Agilent technologies and CST Microwave Studio to do comparison of simulation results. The simulated results comparison gave good results and an agreement between ADS and CST, which confirms the theory and validates the proposed coupler design. After this validation into simulation, we have achieved and tested this coupler, the good agreement between simulated and measured results permits to validate the designed coupler structure. © 2016 IAMOT. Source


Sardi A.,Hassan 1st University of Settat | Zbitou J.,Hassan 1st University of Settat | Errkik A.,Hassan 1st University of Settat | El Abdellaoui L.,Hassan 1st University of Settat | And 2 more authors.
International Conference on Multimedia Computing and Systems -Proceedings | Year: 2014

this paper presents a novel design of branch line (3dB, 90°) coupler, it is designed and simulated by using FR4 substrate at the operating frequency 2.45 GHz in the ISM 'Industrial Scientific Medical' band. The design is based on two different models, the T-model and combinational-model (T- and π-model). After a theoretical study on the use of open stubs, we present the simulation results of this branch line coupler by using the ADS from Agilent technologies and CST Microwave Studio. Good agreement is found between simulated results using ADS and CST Microwave Studio. © 2014 IEEE. Source


Sardi A.,Hassan 1st University of Settat | Zbitou J.,Hassan 1st University of Settat | Errkik A.,Hassan 1st University of Settat | EL Abdellaoui L.,Hassan 1st University of Settat | And 2 more authors.
International Journal of Microwave and Optical Technology | Year: 2014

This paper presents a novel design of branch 3dB coupler, it is designed and simulated by using FR4 substrate at the operating frequency 2.45GHz in the ISM "Industrial Scientific Medical" band. The design is based on two different models, the T-model and combinationalmodel (T- and π-model) in order to reduce the size and improve the performances. After a theoretical study on the use of open stubs, we present the simulation results of this branch line coupler by using ADS from Agilent technologies and CST Microwave Studio. Good agreement is found between simulated and measured results. © 2014 IAMOT. Source


El Hamraoui A.,Hassan 1st University of Settat | Abdelmounim E.,Hassan 1st University of Settat | Zbitou J.,Hassan 1st University of Settat | Tajmouati A.,LITEN Laboratory | And 3 more authors.
Proceedings - 2015 3rd International Workshop on RFID and Adaptive Wireless Sensor Networks, RAWSN 2015 - In conjunction with the International Conference on NETworked sYStems, NETYS 2015 | Year: 2015

This paper presents a novel dual-band uniplanar monopole antenna fed by Coplanar Waveguide (CPW) line suitable for Radio Frequency Identification (RFID) applications especially designed for RFID readers and it operates at 2.45 GHZ and 5.8 GHZ. This antenna is designed with reasonable gain, low profile and low cost achievement. The proposed antenna benefits from the advantages of the CPW line to simplify the structure of the antenna into a single metallic level, hence making it easier for integration with integrated microwave circuits. The simulation results carried out by ADS from Agilent technologies and CST Microwave Studio electromagnetic solvers, demonstrate that we have good performances in term of return loss, gain, radiation pattern and efficiency for the desired frequency bands. This antenna has a total area of 30×45mm2 and mounted on an FR4 substrate with constant dielectric permittivity 4.4 and thickness of 1.6mm and loss tangent of 0.025. The simulated return loss less than -10 dB at the lower band is about 200 MHz and for the upper band reaches about 400 MHz, which covers the RFID standards. The gain obtained into simulation of this antenna is 1,9 dB at 2.45GHz and 2,8 dB at 5.8 GHz. © 2015 IEEE. Source

Discover hidden collaborations