The master’s thesis deals in first part with the design of a single antenna element of an antenna array for receiving the digital TV. The resonant frequency of the antenna is 4.7 GHz, the antenna operates in the frequency band 4.4 to 5.0 GHz. Properties of the antenna are verified in programs CST Microwave Studio and Ansoft Designer. The final antenna element is experimentally produced. The second part is devoted to microstrip divider, 2x2 elements antenna array and 4x4 elements antenna array. The antenna array 4x4 elements was produced and its properties were measured.

This master’s thesis is focused on the properties and types of helical antennas. The helical antenna work in the different modes. These modes are described in this thesis. There are also discussed possibility for design a dual-band helical antennas. The main aim of this work is the selection of a suitable solution and design a dual-band helical antenna for the WiFi band working at resonance frequencies of 2,4 GHz and 5 GHz. The simulation of this antenna was performed in the program CST Microwave studio.

This master’s thesis describes the theoretical analysis of the Sierpinski triangle structure. On the basis of this structure, a planar version of the Sierpinski monopole is firstly designed. Then, by using a transfer of the planar motive to the conical surface, conical and cascade Sierpinski monopoles are designed. All simulations are calculated by CST Microwave Studio 2011. In the thesis, four types of cascade Sierpinski monopole are proposed. The investigated parameters are reflection coefficient, input impedance, radiation properties, polarization and bandwidth. The attention is primarily focused on the design and experimental verification of the selected conical shape cascade Sierpinski monopole set on the bands GSM 900, GSM 1800 and Wi-fi 2,4 GHz.

This thesis deals with the design of omnidirectional monopole antennas. Using the parabolic reflector and the directors, the directional characteristics of monopole antennas are modified. This directional antenna, together with the omnidirectional antenna, examines the effect of various materials, the emission characteristics and the input reflection factor, near the antennas. These antennas are made of 3D textile, measured in anechoic chamber and compared to the designed antennas. At the end of the thesis is the summary and evaluation of the result.

Fast switching operations in IGBTs generate electromagnetic field disturbances, which might cause EMI and functionality issues. For higher frequency characterization, the parasitic inductances and capacitances have to be considered. The characterization of the electromagnetic field disturbances in- and around the converter module could be predicted early in the design. The study involves a high frequency characterization of electric fields (Efield), magnetic fields (H-fields) and the surface currents distribution in a converter module. The high frequency electromagnetic software (CST) was used for the analysis. A given 3D CAD model of an AC/DC converter module was analyzed in CST. The CAD contained IGBT bus-bars interconnections, converter casing, heat sink and other metallic structures. The ACside has six IGBTs and the DC-side has a chopper which has two switches. The IGBTs ONstate and OFF state was modeled with lumped elements. The DC link capacitor was just modeled as lumped elements, while the metallic capacitor casing was included in the 3D model for analyzing the field distribution inside the converter casing. To check the model accuracy, CST models were compared with PEEC (Partial Element Equivalent Circuit) models for simple antenna cases. Using the converter geometry, CST estimates the parasitics and the eventual current, voltage and electromagnetic field distributions for a given excitation signal. The DC-link was excited with a step pulse and the fields were computed. With consideration of specific design details, the modeling approach developed in this study, could be used to construct high frequency models of converter modules for different projects.

This PhD project studied the caesium and strontium removal capacities of six nanoporous materials. Indeed, it was linked in with the SIXEP plant present at Sellafield site, UK, which is currently using natural clinoptilolite, originally mined from the Mojave Desert, to remove radioactive caesium and strontium ions from wastewater effluents. At the moment the feeds entering the SIXEP plant correspond to the best working conditions for clinoptilolite. As the feeds are moving toward more acidic pH and complex solutions and as clinoptilolite works at neutral pH, new nanoporous materials are required. This project had been divided into sub-projects, which all had the same purpose of finding the best material for caesium and strontium removal under complex solutions. The first part of the PhD focused on the synthesis of CST, SNT, ETS-4 and ETS-10 materials following literature reviews. The two last materials studied were provided by Fortum Power and Heat Oy for CsTreat material and by Sellafield Ltd for clinoptilolite material. The second part of the PhD consisted in studying the exchange capacities for caesium and strontium ions for each material studied under batch conditions using several water compositions relevant to Sellafield Ltd. Each water composition had different competing ions or pH and were used to classify the materials between them. From that it was found that Clinoptilolite stays the best materials for caesium and strontium removal. The third part of the project was the gamma irradiation of the materials. This irradiation had an aim to check the stability of the structure of the studied materials under gamma irradiation. The materials were exposed to four different gamma doses which were 0.5; 1; 3 and 6 MGy, the last one corresponding to the maximum dose were structural changes could happen. This revealed that all the materials, except ETS-4 material, were stable under gamma irradiation and that no structural changes were observable. The fourth part of the project was an extension of the third part in which the materials were Cs exchanged before being gamma irradiated to a dose of 6 MGy. This showed that the caesium exchange process is not affected by radiation. Finally, the unexchanged materials were alpha irradiated using a 15 MeV He2+ beam at the Dalton Cumbria Facility. Two irradiations were performed on CsTreat, CST, ETS-4, ETS-10 and clinoptilolite material. It was found that all the materials were damaged by alpha irradiation and displayed amorphous framework To resume, it appeared that clinoptilolite still stays one of the best materials for the removal of caesium and strontium ions in a wide range of wastewater composition. Additionally, it was discovered that ETS-10 material could be a good alternative to clinoptilolite material as its structure is stable under gamma irradiation and it displayed good exchange capacities when competing ions were present in the feeds. CST could also be a substitute as it shows good ion exchange properties under a broad range of pH. SNT material was great for strontium removal while CsTreat was working well for caesium removal. Even though ETS- 4 revealed good ion exchange capacities they were lower than clinoptilolite, ETS- 10 or CST materials.

<p>As the interest in intentional electromagnetic interference (IEMI) increases, so does the need of a suitable antenna which endures those demanding conditions. The ultrawideband (UWB) technology provides an elegant way of generating high-voltage UWB pulses which can be used for IEMI. One UWB antenna, invented solely for the purpose of radiating pulses, is the impulse radiating antenna (IRA). In the course of this master thesis work, a suitable geometry of the IRA is suggested, and modelled, for the high-voltage application of 90 kV.</p>

As the interest in intentional electromagnetic interference (IEMI) increases, so does the need of a suitable antenna which endures those demanding conditions. The ultrawideband (UWB) technology provides an elegant way of generating high-voltage UWB pulses which can be used for IEMI. One UWB antenna, invented solely for the purpose of radiating pulses, is the impulse radiating antenna (IRA). In the course of this master thesis work, a suitable geometry of the IRA is suggested, and modelled, for the high-voltage application of 90 kV.

Le wind-up est une augmentation progressive, fréquence dépendante, de la réponse d'un neurone lors de l'application répétitive de stimuli électriques nociceptifs identiques sur un même territoire. Ce phénomène est essentiellement exprimé par les neurones WDR de la moelle comme du trijumeau. Il dépend en partie de l'activation des récepteurs NMDA et NK1. Il est apparenté chez l'homme à la sommation temporelle et a des conséquences sur la perception de la douleur. Sa signification fonctionnelle n'est pas encore clairement établie. Chez le rat anesthésié et au sein du complexe sensitif du trijumeau, l'objectif de ce travail est : 1) d'analyser les caractéristiques et la fonction du wind-up des neurones WDR trigéminaux, 2) d'identifier les réseaux neuronaux sous tendant le wind-up et 3) d'établir le rôle des rNMDA et des rNK1 dans le wind-up. Nous avons adopté une approche électrophysiologique lors d'enregistrements extracellulaires au sein du Sp5O associés à des micro injections dans le Sp5C. De plus, une approche neuroanatomique a permis d'identifier des réseaux d'interneurones véhiculant le message depuis le Sp5C vers le Sp5O. 1) le wind-up des neurones WDR du Sp5O dépend de l'intensité de la stimulation nociceptive et permet d'améliorer les capacités de codage de stimuli nociceptifs de courte durée. Par ailleurs, nous montrons que le wind-up entraine une modification transitoire (environ 2min) de l'excitabilité des neurones WDR. Cette modification d'excitabilité générée par la wind-up est responsable uniquement de la facilitation des réponses évoquées par la mise en jeu des fibres C. Nous suggérons que l'augmentation de l'excitabilité centrale générée par le wind-up et la sensibilisation centrale sont des phénomènes différents. 2) le wind-up dépend de l'activation des rNMDA locaux alors qu'il est soumis à une inhibition via les rNMDA situés dans les couches superficielles du Sp5C. Le modèle trigéminal permet donc de montrer que, dès l'étage segmentaire, il existe un ajustement permanent de l'amplification du message douloureux. 3) enfin, le développement du wind-up dépend également de l'activation des rNK1 situés sur des interneurones localisés dans la couche III du Sp5C. En conclusion, il apparaît que le wind-up est un phénomène segmentaire permettant le codage de stimulations nociceptives de courte durée et sous tendu à la mise en jeu de voies polysynaptiques rNK1 et rNMDA dépendantes.

This thesis deals with the critical systems thinking (CST) and its necessity and usability within a commercial company. Critical systems thinking is defined and explained from different perspectives, first as a specific way of approaching a problem, but as a tool for problem solving as well. The thesis also details the specific skills of critical systems thinking and systems archetypes and identifies some interrelations between CST and a specific commercial company with its needs. The practical part is focused on the process of solving specific problems using critical systems thinking, it also discusses the benefits and limitations and evaluates the overall necessity of CST for a commercial company.