Σκοπός αυτής της διπλωματικής είναι η μελέτη, σχεδίαση και εξομοίωση κεραιών σχισμής τα χαρακτηριστικά των οποίων τις καθιστούν κατάλληλες για φορητές τερματικές συσκευές. Στο πρώτο κεφάλαιο γίνεται μια σύντομη αναφορά σε βασικές έννοιες της θεωρίας κεραιών, στις ηλεκτρικά μικρές κεραίες αλλά και στην αρχή του Babinet. Στόχος αυτού του κεφαλαίου είναι να συμβάλλει στην καλύτερη κατανόηση του περιεχομένου των επόμενων κεφαλαίων. Στο δεύτερο κεφάλαιο παρατίθενται κάποιες από τις πιο ευρέως διαδεδομένες υπάρχουσες γεωμετρίες κεραιών σχισμής, οι οποίες κατηγοριοποιούνται κυρίως ως προς το εύρος του φάσματος λειτουργίας τους. Στο τρίτο κεφάλαιο μελετάται μια βασική κεραία σχισμής, η κεραία ορθογώνιας σχισμής με τροφοδοσία συνεπίπεδου κυματοδηγού αλλά και μια πολύ ενδιαφέρουσα παραλλαγή της η οποία περιλαμβάνει ένα ζεύγος ορθογώνιων παρασιτικών στοιχείων. Στο τέταρτο κεφάλαιο μελετώνται οι κεραίες σχισμής μονής ζώνης λειτουργίας. Στα πλαίσια αυτής της μελέτης παρουσιάζονται συγκριτικά τα αποτελέσματα από τη σχεδίαση και εξομοίωση μιας κεραίας ζεύγους σχισμών σχήματος δακτυλίου και σχήματος κύκλου αντίστοιχα. Στο πέμπτο κεφάλαιο μελετώνται οι κεραίες σχισμής διπλής ζώνης λειτουργίας. Για το σκοπό αυτό σχεδιάστηκαν και εξομοιώθηκαν μια κεραία ζεύγους σχισμών σχήματος μονόπολου και μια κεραία σχισμής σχήματος βρόχου. Το περιεχόμενο του έκτου κεφαλαίου είναι η ανάλυση της συμπεριφοράς των κεραιών σχισμής ευρυζωνικής λειτουργίας. Αυτό επιτυγχάνεται μέσα από την μελέτη μιας κεραίας ρομβοειδούς σχισμής με ζεύγος μεταλλικών παρασιτικών στοιχειών, μια κεραία τοξοτής σχισμής καθώς και μια κεραία τριγωνικής σχισμής με ζεύγος τροφοδοσίας. Στο έβδομο κεφάλαιο μελετώνται οι υπερευρυζωνικές κεραίες σχισμής. Για το σκοπό αυτό σχεδιάστηκαν και εξομοιώθηκαν μια κεραία ελλειπτικής σχισμής με τροφοδοσία συνεπίπεδου κυματοδηγού και μια κεραίας ελλειπτικής σχισμής με στέλεχος προσαρμογής σχήματος U. Το όγδοο κεφάλαιο που έχει ως στόχο την μελέτη των κεραιών σχισμής που χρησιμοποιούνται σε χιλιοστομετρικές εφαρμογές περιλαμβάνει τα αποτελέσματα της σχεδίασης και εξομοίωσης μιας κεραίας κυκλικής σχισμής με τροφοδοσία μικροταινιακής γραμμής μεταφοράς. Τέλος στο ένατο κεφάλαιο γίνεται μια συνοπτική παρουσίαση των αποτελεσμάτων και παρατίθενται συμπεράσματα και προτάσεις για μελλοντική ενασχόληση στην περιοχή των κεραιών σχισμής. / This diploma thesis includes the analysis, design and simulation of slot antennas for portable terminal devices. In this thesis is presented a variety of slot antennas including single and dual band slot antennas, wideband and ultra wideband antennas as well as slot antennas for millimetre-wave applications.

Thesis concentrates on the problem of gambling on the second grade of the basic school. Thesis consists of two parts " theoretical and practical. The theoretical part is target on characterising of the term dependency and characterise causes and conditions of the dependency inception. Thereinafter the thesis target on the diagnostic of dependencies for basic school teachers and their managing of problems with the dependency. The thesis tries to find out possibilities and efficiency of the prevention on the basic school. In more details focus this thesis on the problem of gambling, its murmurs, causations and possibilities of detoxification. At the close of this thesis is situated the actual state evaluation of gambling in the Czech Republic. The practical part attend to actual state of gambling on the second grade of basic schools. The main part theoretical parts concentrates on questionnaire evaluation, shows differences between big town, small town and a village. This practical part contains also statistical calculations.

The near-miss effect has been demonstrated to maintain gambling behavior by producing physiological changes or thoughts that an individual has "almost won" or was "close" to a winning outcome when, in fact, they lost. Participants were asked to rate each outcome presented on a 10-point Likert scale regarding how close they perceived an outcome was to a win on an automated slot machine created on a Visual Basic program. Data was analyzed for differences between similar outcomes presented with and without an auditory stimulus. Near-miss outcomes presented with an auditory stimulus were rated significantly higher than near-miss outcomes without an auditory stimulus on average across participants. Implications may reveal the effects auditory stimuli on modernized slot machines have on gambling behavior and options for treatment.

Between 1% and 1.4% of people who engage in gambling behaviors lead to disordered or pathological gambling (Whiting & Dixon, 2015), while 44% of all money spent on legal gambling is done so with slot machines (Choliz, 2010). Various behavioral concepts have been theorized as a possible source of gambling addition; losses disguised as wins (LDWs), near-miss, gamblers’ fallacy, illusions of control, and verbally constructed self-rules related to these topics. The current study sought to extend the previous research on condition discrimination in altering slot machine preference while also analyzing the effects of vocalized self-rules during slot machine selection. Conclusions are drawn regarding results comparing cumulative selection to various vocal statement categories. Limitations are expressed and future research is suggested.

Negative expected values typically define the behavior of gambling whereby a person risks more money than probabilistically will be returned. Modern slot machines represent the most popular topography of site gambling, and are thought to encourage irrational gambling behaviors through the presentation of outcome stimuli that occasion the gambler to inaccurately detect the programmed contingencies. One recently added characteristic of modern slot machines is the ability to deliver wins with lower magnitudes of credits than the initially staked wagers. Termed a "loss disguised as a win" (LDW), this type of consequence appears to produce reinforcement effects despite representing an overall loss of credits. In a series of three experiments using computer simulated slot machines, the presentation of LDWs were initially evaluated for possible influence on the temporal characteristics of repeated wagers, subsequently examined to potentially bias response allocation across concurrently available LDW display densities, and finally appraised after discrimination training designed to potentially alter the discriminative and consequential functions of LDWs. Treatment implications and directions for future research are discussed.

Laser cleaning is a non contact, highly controllable process for the removal of contaminants from a surface with minimum or no damage to the substrate material. Laser cleaning has been applied mainly on flat and curved surfaces. Little is known on the phenomena and feasibility of laser cleaning of slotted structures. Slots are common structures in engineering, and can be found in many components. In this PhD work, the feasibility of laser cleaning of alpha case on flat titanium alloy surfaces was initially explored, and then an investigation was made on the use of a pulsed laser for the cleaning of micro to macro slots in silicon and metallic materials. The effects of laser processing parameters on the contaminant removal from these slots were experimentally studied. Laser cleaning thresholds and cleanliness was examined. Meanwhile, finite element modelling (FEM) and time domain finite difference modelling techniques were used to simulate the processes involved to aid the understanding of the technique for process optimisation. The experiments were undertaken to verify if such models are able to accurately predict the cleaning thresholds. The surface and sub-surface characteristics before and after laser cleaning were examined using optical microscopy and scanning electron microscopy (SEM). It has been shown that the slot structure and its material properties were not damaged or changed by laser cleaning process. A novel contribution is that surface morphology after the laser ablation could be used as a diagnostic method to indentify the presence of alpha case and measure its thickness due to the specific characteristics of the surface roughness and generated cracks on the ablated surface after laser irradiation. Besides, it has been found that an axial beam which propagates into the narrow slots can successfully clean the tiny particles on the slot sidewalls whose width ranges from 3.5 mm to 13mm. These phenomena had never been reported before.

In light of incidents and concerns regarding the vulnerability of the global positioning system (GPS), the main purpose of the thesis is to look at alternative systems for radio guidance and to put up a serious study on such alternatives with receive and transmit antenna. There is also the need to design such antennas with multiple frequencies to offer robustness in the unlikely event that such adversarial attacks on the GPS happen. The basis on which such alternative antennas are designed is a slotted microstrip. The characteristics of the slot or slots on the microstrip are analyzed by mapping their exact locations on the patch and then noting the resultant center frequencies, the return losses, and the bandwidth. The activities associated with this also focus on the design, fabrication, validation, and characterization of one or more slotted antennas prototypes. The measurement of the antenna prototypes does confirm several frequencies that coexist to see applications, in aeronautical radionavigation, fixed-mobile radionavigation, and radiolocation. The antennas could also feature in a wide-area augmentation system (WAAS), satellite ground link system (SGLS) as well as in surveillance and precision approach radars. Some variations of the antenna are deployed in the areas of law enforcement, surveillance, and unmanned aerial vehicle (UAV). Applications of the antenna in an unmanned ground vehicle (UGV) are feasible due to its multiple resonant frequencies. Radiolocation and radionavigation antennas have also been known to be mounted in UAVs or on tethered balloons along the borders of the United States to detect low-flying aircraft in support of drug interdiction programs.

Le mélange de fluides représente un élément important du domaine de la dynamique des fluides, ce qui rend la compréhension de ce sujet si significative du point de vue fondamental et appliqué (p. ex., les processus industriels). Dans les géométries miniaturisées (dans des conditions typiques) le mélange est un processus lent, difficile et inefficace. Cela en raison du caractère naturellement laminaire de ces écoulements, qui oblige l'homogénéisation de différents éléments fluides à se produire par diffusion moléculaire au lieu d'un transport advectif, à l'action plus rapide. Cependant, des études expérimentales récentes sur les écoulements viscoélastiques à faible nombre de Reynolds ont montré qu'un mélange efficace peut être déclenché dans plusieurs configurations géométriques (y compris les dispositifs à l'échelle microscopique), par le phénomène de la turbulence élastique. La première partie de cette thèse est consacrée à la compréhension et à l'investigation des défis numériques présents dans le domaine de la dynamique des fluides non newtonienne, en se concentrant plus particulièrement au problème du haut nombre de Weissenberg. Ce dernier se manifeste par une rupture du schéma numérique, lorsque les équations d'évolution d'extra-contraintes polymériques sont évaluées de façon directe. Ceci pose des limites importantes à la possibilité de simuler avec précision des écoulements turbulents-élastiques. Nous fournissons des preuves numériques de l'effet bénéfique (en termes de gain en stabilité) de la décomposition en racine carrée de l'extra-contrainte dans une implémentation en volumes finis des équations régissant l'écoulement dans un canal bidimensionnel. La deuxième partie de la thèse traite de l’émergence et de la caractérisation d’instabilités purement élastiques dans des simulations numériques de fluides Oldroyd-B à nombre de Reynolds zéro dans une géométrie du type cross-slot bidimensionnel. Grâce à un travail numérique approfondi, nous présentons une caractérisation détaillée des instabilités purement élastiques. Ces instabilités apparaissant dans le système pour de larges plages d'élasticité du fluide et de concentration des polymères. Pour les solutions concentrées et des nombres de Weissenberg assez grands, nos simulations indiquent l’apparition d’un écoulement désordonné pointant vers la turbulence élastique. Nous analysons le passage à une dynamique irrégulière et caractérisons les propriétés statistiques de tels écoulements très élastiques, en discutant des similitudes et des différences avec les résultats expérimentaux de la littérature. / Fluid mixing represents an important component of the field of fluid dynamics, what makes the understanding of this subject so meaningful from both the fundamental and applied (e.g. industrial processes) point of view. In miniaturised geometries, under typical conditions, mixing is a slow, difficult and inefficient process due to the naturally laminar character of these flows, which forces the homogenisation of different fluid elements to occur via molecular diffusion instead of faster-acting advective transport. However, recent experimental studies on low-Reynolds-number viscoelastic flows have shown that efficient mixing can be triggered in several geometrical configurations (including micro-scale devices), by the phenomenon of elastic turbulence. The first part of this thesis is devoted to the understanding and investigation of numerical challenges present in the domain of non-Newtonian fluid dynamics, focusing in particular on the high-Weissenberg number problem. The latter manifests as a breakdown of the numerical scheme when the polymeric extra-stress evolution equations are implemented in a direct way, which poses severe limits to the possibility to accurately simulate elastic turbulent flows. We provide numerical evidence of the beneficial effect (in terms of increased stability) of the square-root decomposition of the extra-stress in a finite-volume-based implementation of the governing equations in a two-dimensional channel. The second part of the thesis reports about the emergence and characterisation of purely-elastic instabilities in numerical simulations of zero-Reynolds-number Oldroyd-B fluids in a two-dimensional cross-slot geometry. By means of extensive numerical work, we provide a detailed characterisation of the purely-elastic instabilities arising in the system for wide ranges of both the fluid elasticity and the polymer concentration. For concentrated solutions and large enough Weissenberg numbers, our simulations indicate the emergence of disordered flow pointing to elastic turbulence. We analyse the transition to irregular dynamics and characterise the statistical properties of such highly elastic flows, discussing the similarities and differences with experimental results from the literature.

The basic cube satellite (CubeSat) is a modern small satellite that has a standard size of about one liter (the 1U CubeSat). Three 1U CubeSats could be stacked to form a 3U CubeSat. Their low-cost, short development time, and ease of deployment make CubeSats popular for space research, geographical information gathering, and communication applications. An antenna is a key part of the CubeSat communication subsystem. Traditionally, antennas used on CubeSats are wrapped-up wire dipole antennas, which are deployed after satellite launch. Another antenna type used on CubeSats is the patch antenna. In addition to their low gain and efficiency, deployable dipole antennas may also fail to deploy on satellite launch. On the other hand, a solid patch antenna will compete for space with solar cells when placed on a CubeSat face, interfering with satellite power generation. Slot antennas are promising alternatives to dipole and patch antennas on CubeSats. When excited, a thin slot aperture etched on a conductive sheet (ground plane) is an efficient bidirectional radiator. This open slot antenna can be backed by a reflector or cavity for unidirectional radiation, and solar cells can be placed in spaces on the ground plane not occupied by the slot. The large surface areas of 3U CubeSats can be exploited for a multifunctional antenna by integrating multiple thin slot radiators, which are backed by a thin cavity on the CubeSat surfaces. Solar cells can then be integrated on the antenna surface. Polarization diversity and frequency diversity improve the overall performance of a communication system. Having a single radiating structure that could provide these diversities is desired. It has been demonstrated that when a probe excites a square cavity with two unequal length crossed-slots, the differential radiation from the two slots combines in the far-field to yield circular polarization. In addition, it has been shown that two equal-length proximal slots, when both fed with a stripline, resonate at a frequency due to their original lengths, and also resonate at a lower frequency due to mutual coupling between the slots, leading to a dual-band operation. The multifunctional antenna designs presented are harmonizations and extensions of these two independent works. In the multifunctional antenna designs presented, multiple slots were etched on a 83 mm x 340 mm two-layer shallow cavity. The slots were laid out on the cavity such when the cavity was excited by a probe at a particular point, the differential radiation from the slots would combine in the far-field to yield Left-Handed Circular Polarization (LHCP). Furthermore, when the cavity was excited by another probe at an opposite point, the slots would produce Right-Handed Circular Polarization (RHCP). In addition, as forethought, these slots were laid out on the cavity such that some slots were close together enough to give Linearly Polarized (LP) dual-band operation when fed with a stripline. This antenna was designed and optimized via computer simulations, fabricated using Printed Circuit Board (PCB) technology, and characterized using a Vector Network Analyzer (VNA) and NSI Far Field Systems.

No / Two Cylindrical Dielectric Resonators DR asymmetrically placed on a thin dielectric substrate and fed by a single rectangular slot for wideband wireless applications are presented. Optimized design procedures were applied within a well-known electromagnetic solver to achieve the improved elements dimensions of the antenna geometry. The simulated and measured results show that the proposed DRA can achieve 29% relative bandwidth at 10 dB return loss covering the spectrum range from 9.62 GHz to 12.9 GHz with a maximum gain of 8 dB.