We calculate the circularly polarized Stokes V(λ) profile for emission lines, formed in hot-star winds threaded with a weak radial magnetic field. For simplicity, the field is treated as a split monopole under the assumptions that it has been radially combed by the wind, and rotation is not playing a central role. Invoking the weak-field approximation, we find that the V(λ) profile has a characteristic “heartbeat” shape exhibiting multiple sign inversions, which might be mistaken for noise in the absence of theoretical guidance. We also conclude that there is a tendency for the V(λ) profile to integrate to zero on each side of the line separately. The overall scale of V(λ)/I(λ) is set by the ratio of the field strength to the flow speed, B/v, characteristic of the line-forming region, and is of the order of 0.1% for a wind magnetic field B ≅ 100G at depths where the wind speed is v ≅ 100 km s−1.

No / This article presents a printed crescent-shaped monopole MIMO diversity antenna for wireless communications. The port-to-port isolation is increased by introducing an I-shaped conductor symmetrically between the two antenna elements and shaping the ground plane. Both the computed and experimental results confirm that the antenna possesses a wide impedance bandwidth of 54.5% across 1.6-2.8 GHz, with a reflection coefficient and mutual coupling better than -10 and -14 dB, respectively. By further validating the simulated and the measured radiation and MIMO characteristics including far-field, gain, envelope correlation and channel capacity loss, the results show that the antenna can offer effective MIMO/diversity operation to alleviate multipath environments.

Yes / Empirical results of an electrically small printed monopole antenna is described with fractional bandwidth of 185% (115 MHz–2.90 GHz) for return-loss better than 10 dB, peak gain and radiation efficiency at 1.45 GHz of 2.35 dBi and 78.8%, respectively. The antenna geometry can be approximated to a back-to-back triangular shaped patch structure that is excited through a common feed-line with a meander-line T-shape divider. The truncated ground-plane includes a central stub located underneath the feed-line. The impedance bandwidth of the antenna is enhanced with the inclusion of meander-line slots in the patch and four double split-ring resonators on the underside of the radiating patches. The antenna radiates approximately omnidirectionally to provide coverage over a large part of VHF, whole of UHF, entire of L-band and some parts of S-band. The antenna has dimensions of 48.32×43.72×0.8 mm3, which is corresponding with the electrical size of 0.235λ_0×0.211λ_0×0.003λ_0, where λ_0 is free-space wavelength at 1.45 GHz. The proposed low-profile low-cost antenna is suitable for application in wideband wireless communications systems. / H2020-MSCA-ITN-2016 SECRET-722424 and UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1

Au-delà de la variété des techniques juridiques réalisant une opération de crédit, le contrat de crédit possède une définition qui lui est propre. Il revêt la forme d'un prêt d'argent, d'une ouverture de crédit, d'un crédit-bail ou d'une location-vente. L'affirmation d'une unité conceptuelle et d'une autonomie de ce contrat spécial implique toutefois de dépasser les problématiques liées à son interdépendance avec le contrat financé, au monopole bancaire et ses nombreuses exceptions, et enfin, à la distinction notionnelle professionnel/consommateur. L'unité fonctionnelle apparaît dans l'adaptation des principes du droit commun des contrats par les règles applicables aux contrats de crédit. Le consensualisme, la liberté contractuelle et la force obligatoire des contrats sont confrontés aux mécanismes caractéristiques des contrats de crédit (formalités, devoir de mise en garde, délai de rétractation, interdépendance, remboursement anticipé, déchéance du terme, etc.). Toutefois, cette unité est mise à mal par le constat de dispositions spécifiques aux contrats de crédit consentis à des consommateurs. / Beyond the diversity of legal techniques aimed at performing a credit operation, the credit agreement has its own unique definition. It can take the form of a money loan, a credit opening, a leasing agreement or a hire purchase. However, claiming the existence of a conceptual unity and autonomy for this special agreement implies going beyond the issues related to its interdependence with financed agreements, to the banking monopoly and its numerous exceptions, and to the distinction to be made between professional and consumer. Functional unity is visible in the adaptation of ordinary law of agreements principles through the rules applicable to credit agreements. Consensualism, contractual freedom and the binding force of agreements are confronted with credit agreements' typical mechanisms (formality, duty to warn, period of withdrawal, interdependence, early repayment, repayment by acceleration, etc.). This unity is nevertheless compromised by the acknowledgement of provisions specific to credit agreements granted to consumers.

Diese Arbeit beschreibt die Suche nach relativistischen magnetischen Monopolen mit dem AMANDA Detektor. Die Methoden der Simulation und der Untergrundseparation werden erläutert. Keine Spuren mit der Signatur eines magnetischen Monopols wurden gefunden. Das sich ergebende Flusslimit von 0.61x10^-16 1/(cm^2 sr s) für Monopole, die sich nahe der Lichtgeschwindigkeit bewegen, liegt um einen Faktor 3-4 besser als die Ergebnisse vergleichbarer Untergrundexperimente und einen Faktor 16 unterhalb der Grenze, die aus der beobachteten Stabilität der galaktischen Magnetfelder liegt. / This thesis describes the search for relativistic magnetic monopoles with the AMANDA detector. The methods of their simulation and their separation from the background are given. No tracks with the signature of a magnetic monopoles are found, resulting in an upper limit on the flux of 0.61x10^-16 1/(cm^2 sr s) for monopoles with velocities close to the speed of light. This is better by a factor of 3-4 compared to results from other underground detectors and a factor of 16 below the limit derived from the observed stability of the galactic magnetic fields.

Au cours de ces dernières années, les communications sans fil connaissent une croissance vertigineuse, avec le développement de standards de communication de plus en plus nombreux, qui ouvrent la voie à de multiples applications telles que : la téléphonie mobile, le biomédical, le maritime, le civil et le militaire. De nos jours, les communications sans fil se sont diversifiées et multipliées. Cela entraîne la conception d’antennes toujours plus innovantes, performantes et de taille de plus en plus réduite (miniaturisation). Le projet FLEXBEA (FLEXible BEAcon) a pour but le développement d’un nouveau concept de balises de détresse miniatures (AIS et COSPAS-SARSAT), faible coût, intégrées dans des équipements de sécurité maritime tels qu’un radeau de survie et un gilet de sauvetage. Ces équipements sont destinés aux professionnels de la mer et aux plaisanciers. L’atout majeur de ce nouveau concept est l’intégration dans des équipements de sécurité maritime d’une fonction de détresse en cas de problème majeur : homme à la mer (MOB, Man OverBoard) par exemple lors d’un naufrage. Différentes antennes ont été étudiées. Nous présentons des antennes planaires (de type dipôle ou monopôle imprimé) développées dans la bande UHF : une solution de dipôle avec brins repliés est proposée afin de réduire l'encombrement, et deux modes d'alimentation (symétrique / dissymétrique) sont comparés. Des exemples d'antenne monopôle sont ensuite présentés avec une modification de leur géométrie (structures de type Bow-tie ou méandre) pour assurer une miniaturisation optimale. Puis les antennes filaires retenues pour le projet, avec une modélisation de ces antennes par un circuit équivalent (RLC). Des formules analytiques sont proposées afin de déterminer les valeurs de composants RLC qui interviennent dans le modèle circuit. Ensuite, nous sommes passés à la conception de l’antenne de la balise. Deux antennes ont été conçues et mesurées. Un monopôle ruban avec introduction de composants localisés pour la balise AIS et COSPAS-SARSAT, et une antenne hélice fonctionnant dans la bande AIS, intégrée dans la balise "SIMY". De nombreuses réalisations et mesures ont été effectuées pour caractériser ses antennes. / Over the last few years, wireless communications have grown dramatically, with the development of more and more communication standards, which open the way to multiple applications such as: mobile telephony, biomedical, maritime, the civilian and the military. Today, wireless communications have diversified and multiplied. This leads to the design of antennas that are always more innovative, more efficient and smaller in size (miniaturization). The FLEXBEA project (FLEXible BEAcon) aims to develop a new concept of low cost miniature distress beacons (AIS and COSPAS-SARSAT) integrated into marine safety equipment such as a life raft and a lifejacket safety. This equipment is intended for professionals of the sea and boaters. The main advantage of this new concept is the integration in maritime safety equipment of a distress function in case of major problem: man overboard (MOB, Man OverBoard) for example during a shipwreck. Different antennas have been studied. We present planar antennas (dipole type or printed monopoly) developed in the UHF band: a dipole solution with folded strands is proposed to reduce the bulk, and two modes of supply (symmetrical / asymmetrical) are compared. Examples of monopole antennas are then presented with a modification of their geometry (Bow-tie or meander type structures) to ensure optimal miniaturization. Then the wired antennas selected for the project, with a modeling of these antennas by an equivalent circuit (RLC). Analytical formulas are proposed to determine the RLC component values ​​involved in the circuit model. Then we went to the design of the beacon antenna. Two antennas were designed and measured. A ribbon monopoly with introduction of localized components for the AIS and COSPAS-SARSAT beacon, and a helix antenna operating in the AIS band, integrated into the "SIMY" beacon. Many achievements and measurements have been made to characterize its antennas.

Although current head imaging technologies such as magnetic resonance imaging (MRI) and computed tomography (CT) are capable of providing accurate diagnosis of brain injuries such as stroke and brain tumour, they have several limitations including high cost, long scanning time, bulky and mostly stationary. On the other hand, radar-based microwave imaging technology can offer a low cost, non-invasive and non-ionisation method to complement these existing imaging techniques. Moreover, a compact and wearable device for microwave head imaging is required to facilitate frequent or real-time monitoring of a patient by providing more comfort to the patient. Therefore, a wearable head imaging device would be a significant advantage compared to the existing wideband microwave head sensing devices which typically utilise rigid antenna structure. Furthermore, the wearable device can be integrated into different microwave imaging setups such as real-time wearable head imaging systems, portable systems and conventional stationary imaging tools for use in hospitals and clinics. This thesis presents the design and development of wearable devices utilising flexible antenna arrays and compact radio frequency (RF) switching circuits for wideband microwave head imaging applications. The design and characterisation of sensing antennas using flexible materials for the wearable head imaging device are presented in the first stage of this study. There are two main variations of monopole antennas that have been developed in this research, namely trapezoidal and elliptical configurations. The antennas have been fabricated using different flexible substrate materials such as flexible FR-4, polyethylene terephthalate (PET) and textile. Wideband performances of the antennas have been achieved by optimising their co-planar waveguide feeding line structures. Importantly, the efficiencies of the fabricated antennas have been tested using a realistic human head phantom by evaluating their impedance matching performances when operating in close proximity to the head phantom. The second stage of the study presents the development of wearable antenna arrays using the proposed flexible antennas. The first prototype has been built using an array of 12 flexible antennas and a conformal absorbing material backed with a conductive sheet to suppress the back lobe radiation of the monopole antennas. Additionally, the absorber also acts as a mounting base to hold the antennas where the wearable device can be comfortably worn like a hat during the measurement and monitoring processes. The effect of mutual coupling between adjacent antennas in the array has been investigated and optimised. However, the use of the absorbing material makes the device slightly rigid where it can only be fitted on a specific head size. Thus, a second prototype has been developed by using a head band to realise a stretchable configuration that can be mounted on different sizes of human heads. Furthermore, due to the stretchable characteristic of the prototype, the antennas can be firmly held in their positions when measurements are made. In addition, fully textile based sensing antennas are employed in this prototype making it perfectly suitable for monitoring purposes. Low cost and compact switching circuits to provide switching mechanism for the wearable antenna array are presented in the third stage of this study. The switching circuit is integrated with the antenna array to form a novel wearable microwave head imaging device eliminating the use of external bulky switching network. The switching circuit has been built using off-the-shelf components where it can be controlled wirelessly over Bluetooth connection. Then, a new integrated switching circuit prototype has been fabricated using 6-layer printed circuit board (PCB) technology. For the purpose of impedance matching for the radio-frequency (RF) routing lines on the circuit, a wideband Microstrip-to-Microstrip transition is utilised. The final stage of this study investigates the efficacy and sensitivity of the proposed wearable devices by performing experiments on developed realistic human head phantoms. Initially, a human head phantom has been fabricated using food-based ingredients such as tap water, sugar, salt, and agar. Subsequently, lamb's brains have been used to improve the head phantom employed in the experiments to better mimic the heterogeneous human brain. In terms of imaging process, an interpolation technique developed using experimental data has been proposed to assist the localisation of a haemorrhage stroke location using the confocal delay-and-sum algorithm. This new technique is able to provide sensible accuracy of the location of the blood clot inside the brain. The wearable antenna arrays using flexible antennas and their integrations with compact and low cost switching circuits reported in this thesis make valuable contribution to microwave head imaging field. It is expected that a low-cost, compact and wearable radar-based microwave head imaging can be fully realised in the future for wide range of applications including static scanning setup in hospitals, portable equipment in ambulances and as a standalone wearable head monitoring system for remote and real-time monitoring purposes.

Une fraction non négligeable de la population mondiale n’a pas accès au crédit, en raison d’une insuffisance de ressources, d’une inscription dans un fichier de surendettement ou de la restriction des critères d’octroi du crédit bancaire. Pourtant, devenus incontournables avec la domiciliation des salaires et des prestations sociales, les produits et les services bancaires participent au processus d’exclusion sociale. Ne pas avoir accès au crédit, ou y avoir accès de manière inadaptée, est, en soi, un facteur d’appauvrissement. Faute d’accès à un prêt personnel ou à un découvert bancaire, de nombreux ménages recourent à des crédits renouvelables dont les conditions d’octroi sont de plus en plus contestées par les pouvoirs publics ; aussi, les risques de surendettement s’en trouvent-Ils accrus. Or, dans le contexte actuel de crise économique, de recrudescence du chômage et des emplois précaires, le recours au microcrédit peut être un outil utile pour répondre aux besoins de réinsertion à travers la création, la reprise ou le transfert d'activités rémunératrices. La conjoncture actuelle semble d'autant plus favorable à un renouveau du microcrédit que celui-Ci peut permettre à l’emprunteur de rebondir en créant sa petite entreprise, ou de s’assumer sans détériorer sa situation financière personnelle. Bien géré, il constitue un facteur d’autonomie de la personne,tout en favorisant une pratique nouvelle de la solidarité par des relations plus ou moins directes entre prêteurs, épargnants et emprunteurs. Il a en quelque sorte un caractère universel qui sied à l’esprit du temps. Actualisé et modernisé dans les pays du Sud, le crédit solidaire nécessite une adaptation du concept dans les pays développés, pour tenir compte de leur contexte. Ainsi, une pratique des pays moins développés est « exportée » vers les pays du Nord, qui redécouvrent des pratiques anciennes — mutualisme, prêt sur gages, tontine,solidarité familiale ou de groupe — dont l’esprit originel s’était estompé avec la modernisation de leur système bancaire ou, tout simplement, leur mode de vie plus individualiste. Beaucoup de débats existent entre économistes sur la réalité de l’efficacité du microcrédit. Bien que celui-Ci soit économiquement et socialement séduisant pour les uns,proprement illusoire pour les autres, le juriste semble être placé hors du débat. Il n’existe pas de vrais débats (en Europe en tout cas) sur les aspects juridiques du microcrédit de sorte qu’on pourrait douter de sa place en droit. Est-Ce à dire que cette belle invention économique a manqué de pénétrer le domaine juridique ? Cette thèse tente de jeter les bases d’un vrai débat juridique sur le phénomène du microcrédit. Elle s'efforce de dresser, juridiquement, un état des lieux du microcrédit, l’offre, la demande, mais aussi les perspectives envisageables pour un développement de la pratique. / All over the world, a significant fraction of the population has no access to credit, due to insufficient resources, a registering in a file of big debts or of restriction criteria for the granting of bank credit. However, now indispensable due to the address of wages and social security benefits, banking services are involved in the process of social exclusion. Not having access to credit, or having access in an inappropriate manner is in itself a factor of impoverishment. Without access to a personal loan or to an overdraft, many households relyon revolving credits whose conditions of granting is increasingly challenged by the authorities, and thus the risk of big debt are there by increased. But in the current context ofthe economic crisis of growing unemployment and of part-Time work, the use of microcreditcan be a useful tool to meet the needs of some households in terms of business start-Ups,business transfers or business continuities. The current environment seems to favor a revivalof microcredit, as it allows the borrower to bounce back and create his or her employment orsmall business, or to support themselves without damaging their personal financialsituation. Properly managed, it is a factor of individual autonomy, while promoting a newpractice of solidarity through more or less direct relationship between lenders, borrowers andsavers. There is a sort of universal character that befits the spirit of time. Modernized andupdated in southern countries, solidarity loan requires an adaptation of the concept indeveloped countries, to take their context into account. Thus, a practice of less developedcountries is "exported" towards western countries, which are rediscovering ancient practices –mutualism, pawnshop, tontine, family or group solidarity – whose original spirit had dimmedwith the modernization of their banking system or, simply, their more individualistic lifestyle.There are many debates between economists about the reality of the effectiveness ofmicrocredit. About microcredit which is economically and socially attractive to some, purelyan illusion for others, the legal representative seems to stand aside from the debate. There isno real debate (at any rate in Europe) on the legal aspects of microcredit in such an extent thatwe might question its position in law. Is it that this wonderful economic invention has failedto enter the legal domain ? Our work aims at laying the groundwork for a real legal debate onthe phenomenon of microcredit. Its ambition is to draw, legally, an overview of themicrocredit, the supply, the demand and also the way forward for the development of thepractice.

Several microwave devices and antennas that are based on negative-refractive-index transmission-line (NRI-TL) metamaterials are presented in this thesis, which exhibit superior performance features compared to their conventional counterparts. These are a Wilkinson balun, a 1:4 series power divider, a four-element printed dipole array, a leaky-wave antenna, and an electrically small folded-monopole antenna. The Wilkinson balun employs +90° and −90° NRI-TL metamaterial lines at the output branches of a Wilkinson divider, to achieve a six-fold increase in the measured differential output phase bandwidth compared to that of an analogous balun employing transmission lines, while occupying only 55% of the area. The 1:4 series power divider comprises four non-radiating 0° NRI-TL metamaterial lines, each with a compact length of λ0/8, to provide equal power split to all four output ports. Compared to a conventional series power divider employing one-wavelength long transmission lines, the metamaterial divider provides a 154% increase in the measured through-power bandwidth, while occupying only 54% of the area. The metamaterial series power dividing concept is also applied to a four-element fully-printed dipole array that is designed to radiate at broadside, in order to demonstrate that the array exhibits reduced beam squinting characteristics. It is shown that the metamaterial-fed array has a measured scan-angle bandwidth that is 173% greater than an array that is fed using a conventional low-pass loaded line. The reduced-beam squinting property that NRI-TL metamaterial lines offer is subsequently exploited to create a leaky-wave antenna that radiates a near-fixed beam in the forward +45° direction, with an average measured beam squint of only 0.031°/MHz. This is achieved by operating the antenna in the upper right-handed band where the phase and group velocities are the closest to the speed of light. Finally, an electrically small antenna comprising four 0° NRI-TL metamaterial unit cells is presented which supports a predominantly even-mode current, thus enabling it to be modeled as a multi-arm folded monopole. This significantly increases its radiation resistance, which allows it to be matched to 50 Ω, while maintaining a high measured efficiency of 70%.

Several microwave devices and antennas that are based on negative-refractive-index transmission-line (NRI-TL) metamaterials are presented in this thesis, which exhibit superior performance features compared to their conventional counterparts. These are a Wilkinson balun, a 1:4 series power divider, a four-element printed dipole array, a leaky-wave antenna, and an electrically small folded-monopole antenna. The Wilkinson balun employs +90° and −90° NRI-TL metamaterial lines at the output branches of a Wilkinson divider, to achieve a six-fold increase in the measured differential output phase bandwidth compared to that of an analogous balun employing transmission lines, while occupying only 55% of the area. The 1:4 series power divider comprises four non-radiating 0° NRI-TL metamaterial lines, each with a compact length of λ0/8, to provide equal power split to all four output ports. Compared to a conventional series power divider employing one-wavelength long transmission lines, the metamaterial divider provides a 154% increase in the measured through-power bandwidth, while occupying only 54% of the area. The metamaterial series power dividing concept is also applied to a four-element fully-printed dipole array that is designed to radiate at broadside, in order to demonstrate that the array exhibits reduced beam squinting characteristics. It is shown that the metamaterial-fed array has a measured scan-angle bandwidth that is 173% greater than an array that is fed using a conventional low-pass loaded line. The reduced-beam squinting property that NRI-TL metamaterial lines offer is subsequently exploited to create a leaky-wave antenna that radiates a near-fixed beam in the forward +45° direction, with an average measured beam squint of only 0.031°/MHz. This is achieved by operating the antenna in the upper right-handed band where the phase and group velocities are the closest to the speed of light. Finally, an electrically small antenna comprising four 0° NRI-TL metamaterial unit cells is presented which supports a predominantly even-mode current, thus enabling it to be modeled as a multi-arm folded monopole. This significantly increases its radiation resistance, which allows it to be matched to 50 Ω, while maintaining a high measured efficiency of 70%.