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Search Results: 1 - 10 of 149915 matches for " H Taoufik "
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Study of the emissivity of rough surfaces periodic using the method of coupled waves analysis (CWA) compared with method of geometrical optics approximation (GOA)  [PDF]
Taoufik Ghabara
Natural Science (NS) , 2011, DOI: 10.4236/ns.2011.31008
Abstract: We present in this paper a numerical study of the validity limit of the geometrical optics approximation compared with a differential method which is established according to rigorous formalisms based on the electromagnetic theory. The precedent studies show that this method is adapted to the study of diffraction by periodic rough surfaces. We determine by two methods the emissivity of gold and tungsten for surfaces with a rectangular or sinusoidal profile, for a wavelength equal to 0.55 microns. The monochromatic directional emissivity of these surfaces clearly depends on the angle of incidence, the surface profile, height, period and the nature of the material. We perform our calculations by a method of coupled wave analysis (CWA) and a geometric optics method (GOA). The latter method is theoretically valid only when the dimensions of the cavities are very large compared to the wavelength, while the CWA is theoretically correct whatever these dimensions. The main purpose of this work is to investigate the validity limit of GOA compared with CWA. The obtained results for a fixed height of the grating, allowed us to delimit the validity domain of the optic geometrical approximation for the treated cases. Finally, the agreement between the emissivity calculated by the differential method and that given on the basis of the homogenization theory is satisfactory when the period is much smaller than the wavelength.
New Formula for Evaluating the Number of Unit Cell of a Finite Periodic Structure Considered as Infinite Periodic One  [PDF]
Samia Bouali, Taoufik Aguili
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2011, DOI: 10.4236/jemaa.2011.39055
Abstract: This paper presents a modeling and an analysis of one-dimensional periodic structure composed of a cascade connection of N cells considered as infinite. The ABCD matrix representations with the Floquet analysis have been used to derive the dispersion relation and input impedance of infinite periodic structure. The transmission matrix for the N identical cascaded cells has been successfully used to obtain an efficient and easy-to-use formula giving the necessary number of cells such that they can be considered infinite. As an illustrative example, the formula is applied and verified to finite size TL periodically loaded with obstacles. Scattering parameters and the input impedance of the structure are expressed and plotted.
Finite Step Conjugate Gradients Methods for the Solution of an Impedance Operator Equation Arising in Electromagnetics  [PDF]
Haifa belhadj, Taoufik Aguili
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2011, DOI: 10.4236/jemaa.2011.310066
Abstract: A class of finite step iterative methods, conjugate gradients, for the solution of an operator equation, is presented on this paper to solve electromagnetic scattering. The method of generalized equivalent circuit is used to model the problem and then deduce an electromagnetic equation based on the impedance operator. Four versions of the conjugate gradient method are presented and numerical results for an iris structure are given, to illustrate convergence properties of each version. Computational efficiency of these methods has been compared to the moment method.
Acacia trotilis and Calotropis procera: Do They Substantially Promote Soil Carbon Sequestration?  [PDF]
Taoufik Saleh Ksiksi
Open Journal of Soil Science (OJSS) , 2012, DOI: 10.4236/ojss.2012.22017
Abstract: Very little is known about the type and mix of desert plant species and their management to optimize carbon sequestration in desert ecosystems. Overgrazing is one important practice that affects soil carbon cycling and therefore sequestration. Improving soil carbon in desert ecosystems may be best through the use of native trees and shrubs. Acacia tortilis and calotropis procera are two important species in the United Arab Emirates (UAE). The former is a native species that improves biodiversity and the latter is not native and has been reported to be an indicator of overgrazing. The average soil organic matter (SOM) content was higher in soils dominated by A. tortilis when compared to those dominated by C. procera; 2.98 and 1.34; respectively (P < 0.05). Moreover, A. tortilis leaves had a higher OM content than C. procera leaves (94.1% and 90.6%; respectively). The higher OM content of A. tortilis leaves explains the higher contribution of this species to the overall soil organic matter inputs. There was also a significant effect of shrub species on total SOC (P < 0.05). A total of about 14.7 tons of SOC were added per hectare in the areas dominated by A. tortilis. While only about 6.6 tons of SOC were added to the areas dominated by C. procera. In short, it is believed that both species substantially promote soil carbon sequestration. Some significant superiority of the native A. tortilis has been shown. But much has to be done to investigate the mix of plant species that promote the best soil carbon sequestration in the desert areas. Further studies are required in order to assess temporal as well as spatial variations in soil carbon sequestration in the UAE deserts. This will certainly help, in addition to other practices, in mitigating CO2 emission.
A New Approach Based on Iterative Method for the Characterization of a Micro-Strip Line with Thick Copper Conductor  [PDF]
Rafika Mejri, Taoufik Aguili
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2016, DOI: 10.4236/jemaa.2016.85010
Abstract: In this work, we applied two electromagnetic models for the characterization of a planar structure including a flat, thick copper conductor. Indeed the first model is consisted by modeling two metal ribbons without bulkiness, placed one above the other at a distance of h2 equal to the thickness of the thick conductor. This approach has been implemented and tested by the iterative method. The results of simulations have been compared with those calculated by the Ansoft HFSS software, and they are in good concordance, validating the method of analysis used. The second model is based on the calculation of the effective permittivity of the medium containing the thick conductor. This medium consists of a metallic region of complex relative permittivity \"\", the rest of this medium is filled with air er2 = 1. The effective permittivity eeff calculated from these two relative permittivity er2 and \"\". Comparing the simulation results of this new formulation of the iterative method with those calculated by the software Ansoft HFSS shows that they are in good matching which validates the second model.
New Formulation of the Mulilayer Iterative Method: Application to Coplanar Lines with Thick Conductor  [PDF]
Rafika Mejri, Taoufik Aguili
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2016, DOI: 10.4236/jemaa.2016.89019
Abstract: The skin effect is an electromagnetic phenomenon that makes the current flows only on the surface of the conductors at high frequency. This article is based on the phenomenon to model a structure made in coplanar technology. In reality, these types of structures integrated metal layers of different thickness of copper (9 μm, 18 μm, 35 μm, 70 μm). The neglect of this parameter introduces errors, sometimes significant, in the numerical calculations. This is why an iterative method (FWCIP) based on the wave concept was restated. Validation of results was carried out by comparison with those calculated by Ansoft HFSS software and Agilent ADS Technology. They show a good matching.
Evaluating Salt Tolerance of 14 Barley Accessions from Southern Tunisia Using Multiple Parameters
Abdennaceur Ben khaled,Taoufik Hayek,Elhem Mansour,Hédia Hannachi
Journal of Agricultural Science , 2012, DOI: 10.5539/jas.v4n12p27
Abstract: Barley “Ardhaoui” (Hordeum vulgare L.) is a local landraces cropped in southern Tunisia characterized by its resistance to drought and salinity. Salt tolerance of barley changes according to the growth stages. In order to study the salinity tolerance of (Hordeum vulgare L.), fourteen barely accessions, were grown in soil and exposed to four salinity levels (5, 7, 13 and 20 dS/m). To evaluate its salt tolerance using multiple parameters, fourteen barley accessions from two regions in the southern Tunisia (costal and mountainous regions) were grown in soil and exposed to four salinity levels (5, 7, 13 and 20 dS/m). Plant growth parameter, total biomass at final harvest, straw yield and yield compound associated with salt tolerance during the different growth stages were determined. The results showed negative effects of salinity on the growth and the development of the barley. However, the salt sensitive accessions showed a greater reduction in tiller number (e.g. by about 80 %) than tolerant ones (e.g. by about 57 %) at 20 dS/m. These decrease on the growth of leaves, tillers and the aerial part constitute a strategy developed by the barely in vegetative phase to reduce the salt stress. Tiller and spikelet numbers were more affected by the salinity at 13 and 20 dS/m the different results showed significant correlation between the spikes numbers and the tiller number (r = 0.872). The salinity affected negatively these two parameters, which both initiate during early growth stages. So, the salinity has a greater influence on final grain yield than on yield components in the later stages. The studied parameters showed significant differences (p<0.05) between the barely accessions. The cluster analysis using agronomic parameters at all growth stage showed that the accessions “Ettalah” and “Elhezma” were ranked as the most tolerant to salinity. However, “Boughrara” and “Edwiret Elgdima” accessions were ranked as moderate and presented a change of their degree of tolerance with the different growth stage. The remaining accessions showed the lowest tolerance to salinity. A highest tolerance was observed on the accessions from plain zones compared at those of mountainous zones. The response differences between accessions of local population of barley “Ardhaoui” reflecting an important internal genetic variability against the salinity. This variability could be more explored and used for the barley breeding program.
Psychogenic Nonepileptic Seizures: What a Neurologist Should Know  [PDF]
Taoufik Alsaadi, Tarek M. Shahrour
Health (Health) , 2014, DOI: 10.4236/health.2014.616241
Abstract: Psychogenic nonepileptic seizures (PNES) are episodes of movement, sensation or behavior changes similar to epileptic seizures but without neurological origin. They are somatic manifestations of psychological distress. The aim of this article is to provide a comprehensive review of the practical aspects of this, most often misdiagnosed disorder, which will be of clinical relevance to all practicing neurologists. Patients with PNES are often misdiagnosed and treated for epilepsy for years, resulting in significant morbidity. Video-EEG monitoring is the gold standard for diagnosis. Five to ten percent of outpatient epilepsy populations and 20 to 40 percent of inpatient and specialty epilepsy center patients have PNES. These patients inevitably have comorbid psychiatric illnesses, most commonly depression, post-traumatic stress disorder (PTSD), other dissociative and somatoform disorders, and personality pathology, especially borderline type. Many have a history of sexual and physical abuse. 75 to 85 percent of patients with PNES are women. Although PNES can occur at any age, they typically begin in young adulthood. Treatment involves discontinuing antiepileptic drugs in patients without concurrent epilepsy and referring for appropriate psychiatric care. Additional larger controlled studies to determine the best treatment modalities are needed.
Synthesis and Optimization of Almost Periodic Antennas Using Floquet Modal Analysis and MoM-GEC Method  [PDF]
Nader Ben Latifa, Taoufik Aguili
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2019, DOI: 10.4236/jemaa.2019.111001
Abstract: This paper presented a new Floquet analysis used to calculate the radiation for 1-D and 2-D coupled periodic antenna systems. In this way, an accurate evaluation of mutual coupling can be proven by using a new mutual interaction expression that was based on Fourier analysis. Then, this work indicated how Floquet analysis can be used to study a finite array with uniform amplitude and linear phase distribution in both x and y directions. To modelize the proposed structures, two formulations were given in a spectral and spatial domain, where the Moment (MoM) method combined with a generalized equivalent circuit (GEC) method was applied. Radiation pattern of coupled periodic antenna was shown by varying many parameters, such as frequencies, distance and Floquet states. The 3-D radiation beam of the coupled antenna array was analyzed and compared in several steering angles θs and coupling values dx. The simulation of this structure demonstrated that directivity decreased at higher coupling values. The secondary lobs in the antenna radiation pattern affected the main lobe gain by energy dispersal and considerable increasing of side lobe level (SLL) may be achieved. Therefore, the sweeping of the radiation beam in several steering directions affected the electromagnetic performance of the antenna system: the directivity at the steering angle θs = π3 was more damaged and had 19.99 dB while the second at θs = 0 had about 35.11 dB. This parametric study of coupled structure used to concept smart periodic antenna with sweeping radiation beam.
Catherine Collomp et Mario Menendéz, dir. Exilés et réfugiés politiques aux Etats-Unis : 1789-2000.
Taoufik Djebali
Transatlantica : Revue d'études Américaines , 2006,
Abstract: Dans cet ouvrage collectif de 16 contributions portant sur les exilés et les réfugiés politiques aux Etats-Unis de 1789 à 2000, C. Collomp et M. Menendez se sont efforcés, dans un souci évident de clarté, d’approfondissement et de cohérence, de présenter un travail à la fois chronologique et thématique. Le grand intérêt de cet ouvrage est l’analyse sans complaisance de la continuité et des changements des perceptions et des politiques concernant les réfugiés aux USA.L’ouvrage commence astucie...
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