Joint Time/Frequency Analysis and Design of Spiral Antennas and Arrays for Ultra-Wideband Applications

Ultra-wideband (UWB) systems transmit and receive extremely short pulses, permitting the corresponding antennas to distort their shape. Thus the design of an antenna for a UWB system plays an important role for the reliability and quality of communication. A UWB antenna design coalesces both the determination of conventional frequency domain parameters and the analysis of time domain response into a single overarching system requirement. While the former is needed to ensure system’s sensitivity, the later is critical to minimize pulse distortion. Well-designed spiral antennas are known for their almost frequency independent characteristics; thus they are viable candidates for UWB systems from the frequency-domain side. However, due to their fundamental principles of operation, they are dispersive and arguments were made they should not be used for pulsed UWB applications (time-domain side). The presented research unequivocally proves that spiral antennas and various derivatives thereof, including arrays, can be excellent candidates for multifunctional time/frequency domain systems. A complete framework for joint frequency and time domain characterization of planar spiral antennas in UWB communication systems is developed first. By utilizing theory, simulations, and experiments, all essential to the analysis frameworks, the various hypotheses are comprehensively treated and relevant conclusions are established. The dispersion and pulse distortion of the conventional spiral antennas are characterized in the radiation and system modes and conclusions regarding the effects of geometrical parameters such as number of arms, mode of operations, etc., on time- and frequency-domain performance are derived for the first time. A method based on controlling the spiral’s growth rate and input pulse shape is demonstrated as an effective approach to reduce the pulse distortion. Theoretical pre-distortion compensation method based on a frequency-dependent delay removal technique is employed and performance enhancement of spiral antennas as pulse radiators is successfully demonstrated. A novel spiral antenna topology, named combined power spiral, is derived from first principles to have simultaneously excellent time- and frequency-domain performances without any auxiliary hardware and/or pre-distortion compensation. The role of the reflective cavity backing on the performance of spiral antennas in time and frequency domains is investigated in order to achieve an efficient unidirectional UWB radiation. Resistively-loaded cavity-backed spirals are designed as a compromise for achieving simultaneously good time and frequency domain performances while maintaining high efficiency over the most of operating bandwidth. The lens loading approach is used as a way to further improve the spiral’s gain and reduce the amplitude distortion associated with a typical communication channel. UWB spiral arrays based on the derived good time/frequency two- and four-arm spiral antennas are developed and analyzed in time and frequency domains. Multi-mode capabilities of four-arm spirals are used to engineer a dual-circularly polarized array embodiment. To make these arrays practically more desirable, novel feeding scheme which significantly reduces the beamformer complexity is proposed. Time and frequency scanning capabilities and the advantages of the proposed arrays for UWB communications are also discussed. The results of this thesis can pave the way for the use of spiral antennas in many non-traditional, for spiral antennas, applications across commercial and military sectors

Antibacterial, Antioxidant and Anti-inflammatory activities of Honey.

Abstract: Honey has been widely characterized as a valued food and a medicine by the humankind since ancient times, traditionally it was used as a nutritious supplement and also to treat a variety of diseases from wound healing to cancer treatment. this therapeutical effects of honey, including antioxidant activity, antibacterial activity and anti-inflammatory activity, is due absolutely to its contents and compounds such as: flavonoids, phenolic compounds, vitamins…  and his physicochemical properties : acidity, osmolality, water activity, hydrogen peroxide activity… Different types of analyzes, either in vivo or in vitro, have been carried out on honeys to prove these activities such as: Radical-scavenging effect on DPPH (2, 2-diphenyl-1-picrylhydrazyl), Radical-scavenging effect on hydroxyl radicals and Radical-scavenging effect on superoxide activity for the antioxidant activity, percentage inhibition against certain bacteria for antibacterial activity and the Inhibition of ROS (Reactive Oxygen Species) and the percentage of Ulcer Index (UI) for anti-inflammatory activity.  

Schottky Diodes and Thin Films Based on Copolymer: Poly(aniline-co-toluidine)

Poly(aniline-co-o-toluidine) (PANI-co-POT) thin films were deposited on indium tin oxide- (ITO-) coated glass substrates by electrochemical polymerization under cyclic voltammetric conditions from aniline-co-o-toluidine monomer in an aqueous solution of HCl as a supporting electrolyte. These measurements showed that the optical band gap of the copolymer films is on the order of 2.65 eV. On the other hand, ITO/PANI-co-POT/Al devices were fabricated by thermal evaporation of Aluminum circular electrodes on the as-deposited PANI-co-POT films. The Current-Voltage characteristics of these devices are nonlinear. The diode parameters were calculated from I-V characteristics using the modified Shockley equation. The C-F characteristics were also measured

Dielectric Behavior of Ceramic (BST)/Epoxy Thick Films

Composite materials were made by mixing powders of Ba1−xSrxTiO3 (x=0.2 and 0.4) ceramics and epoxy resin with various volume fractions (vol%). Dielectric measurements of these composites were performed as a function of filler ratio in the range 100–360°K at 10 KHz. The dielectric constant of the composite increased with increasing volume fraction varies slightly with temperature. The 20 vol% of BST(0.4)-epoxy composite had the highest dielectric constant of 19.4 and dielectric loss tangent of 0.027. Among the dielectric mixing models presented, the model of Lichtenecker shows the best fit to the experimental data for both composites

The benefits of being a near-peer teacher

Background: Near-peer teaching is used in anatomy education because of its benefits to the learner, teacher and faculty. Despite the range of reports focusing on the learner, the advantages for the teacher, which are thought to include communication skills, subject knowledge and employability, are only beginning to be explored. Method: A questionnaire was distributed to the teachers involved in anatomy near-peer teaching at the University of Southampton and Brighton and Sussex Medical School. This questionnaire was designed using 0-10 rating scales to assess teacher perspectives on their level of knowledge, teaching skills and enjoyment of teaching. Free text responses determined the teachers’ motivation and perceived benefits from the teaching. Results: Twenty-eight questionnaires were gathered (54.9% response rate) including 20 from Southampton and 8 from BSMS. Long term knowledge retention and better understanding of the material were rated 8.1 and 7.9 out of 10 respectively. Eight responses were from currently practising doctors, who rated how much they now use their teaching skills as doctors as 8.9 out of 10. Of the 8 doctors, 7 gained points for their foundation programme applications as a direct result of near-peer teaching. The most common motivator for engaging in teaching was to improve subject matter knowledge and the most common benefit was improved communication skills. Discussion: There are numerous advantages to being a near-peer teacher in medical school, which include knowledge improvement, transferrable professional skills and employability. These initial results support the hypothesised benefits to the teachers and provide a foundation for further longitudinal studies

Model checking and code generation for UML diagrams using graph transformation

UML is considered as the standard for object-oriented modelling language adopted by the Object Management Group. However, UML has been criticized due to the lack of formal semantics and the ambiguity of its models. In other hands, UML models can be mathematically verified and checked by using its equivalent formal representation. So, in this paper, we propose an approach and a tool based on graph transformation to perform an automatic mapping for verification purposes. This transformation aims to bridge the gap between informal and formal notations and allows a formal verification of concurrent UML models using Maude language. We consider both static (Class Diagram) and dynamic (StateChart and Communication Diagrams) features of concurrent object-oriented system. Then, we use Maude LTL Model Checker to verify the formal model obtained (Automatic Code Generation Maude). The meta-modelling AToM3 tool is used. A case study is presented to illustrate our approach.030

Hépatite stéatosique non alcoolique: physiopathologie et profils anatomopathologiques et évolutifs

La stéatohépatite non alcoolique (NASH) est une stéatose hépatique non associée à l’alcoolisme. C’est une affection très fréquente surtout dans les pays développés liés à l’obésité. Elle est le plus souvent de découverte fortuite devant une perturbation du bilan hépatique qui permet d’orienter le diagnostic .Ce dernier est confirmé devant la présence de trois éléments : L’absence d’alcoolisme, l’absence d’une cause d’hépatopathie chronique et la présence de lésions histopathologiques hépatiques sur biopsie hépatique à type de stéatose, hépatite ou de fibrose. Elle est associée de façon systématique avec un syndrome d’insulinorésistance.Son évolution se fait vers une fibrose septale étendue et la cirrhose dans la majorité des séries.Le traitement de la NASH n’est pas bien codifiée pour le moment