El objetivo del trabajo es presentar rasgos temáticos y estilísticos de la poesía de Thom Gunn. Este es un poeta británico y lo he elegido por su prolífica obra, en la cual se integran temáticas culturales y políticas como parte de su carrera como poeta. Desde sus comienzos como estudiante de Cambridge, "de algún modo, el carácter y la máscara de los poemas de Gunn es lo que Christopher Isherwood definió como "El Hombre Realmente Débil", que siempre toma una vía circular y más peligrosa porque no puede enfrentarse a decisiones tajantes que lo lanzarían a un viaje mucho más directo. Estas consideraciones hacen que Gunn sea un poeta sumamente interesante desde una perspectiva filosófica

El objetivo del trabajo es presentar rasgos temáticos y estilísticos de la poesía de Thom Gunn. Este es un poeta británico y lo he elegido por su prolífica obra, en la cual se integran temáticas culturales y políticas como parte de su carrera como poeta. Desde sus comienzos como estudiante de Cambridge, "de algún modo, el carácter y la máscara de los poemas de Gunn es lo que Christopher Isherwood definió como "El Hombre Realmente Débil", que siempre toma una vía circular y más peligrosa porque no puede enfrentarse a decisiones tajantes que lo lanzarían a un viaje mucho más directo. Estas consideraciones hacen que Gunn sea un poeta sumamente interesante desde una perspectiva filosófica

Thesis (DTech (Electrical Engineering))--Cape Peninsula University of Technology, 2017. / Gunn diodes play a prominent role in the development of low-cost and reliable solid-state oscillators for diverse applications, such as in the military, security, automotive and consumer electronics industries. The primary focus of the research presented here is the optimisation of GaAs and GaN Gunn diodes for mm-wave operations, through rigorous Monte Carlo particle simulations. A novel, empirical technique to determine the upper operational frequency limit of devices based on the transferred electron mechanism is presented. This method exploits the hysteresis of the dynamic velocity-field curves of semiconductors to establish the upper frequency limit of the transferred electron mechanism in bulk material that supports this mechanism. The method can be applied to any bulk material exhibiting negative differential resistance. The simulations show that the upper frequency limits of the fundamental mode of operation for GaAs Gunn diodes are between 80 GHz and 100 GHz, and for GaN Gunn diodes between 250 GHz and 300 GHz, depending on the operating conditions. These results, based on the simulated bulk material characteristics, are confirmed by the simulated mm-wave performance of the GaAs and GaN Gunn devices. GaAs diodes are shown to exhibit a fundamental frequency limit of 90 GHz, but with harmonic power available up to 186_GHz. Simulated GaN diodes are capable of generating appreciable output power at operational frequencies up to 250 GHz in the fundamental mode, with harmonic output power available up to 525 GHz. The research furthermore establishes optimised doping profiles for two-domain GaAs Gunn diodes and single- and two-domain GaN Gunn diodes. The relevant design parameters that have been optimised, are the dimensions and doping profile of the transit regions, the width of the doping notches and buffer region (for two-domain devices), and the bias voltage. In the case of GaAs diodes, hot electron injection has also been implemented to improve the efficiency and output power of the devices. Multi-domain operation has been explored for both GaAs and GaN devices and found to be an effective way of increasing the output power. However, it is the opinion of the author that a maximum number of two domains is feasible for both GaAs and GaN diodes due to the significant increase in thermal heating associated with an increase in the number of transit regions. It has also been found that increasing the doping concentration of the transit region exponentially over the last 25% towards the anode by a factor of 1.5 above the nominal doping level enhances the output power of the diodes.

The mm-wave frequency range is being increasingly researched to close the gap between 100 to 1000 GHz, the least explored region of the electromagnetic spectrum, often termed as the 'THz Gap'. The ever increasing demand for compact, portable and reliable THz (Terahertz) devices and the huge market potential for THz system have led to an enormous amount of research and development in the area for a number of years. The Gunn Diode is expected to play a significant role in the development of low cost solid state oscillators which will form an essential part of these THz systems.Gunn and mixer diodes will 'power' future THz systems. The THz frequencies generation methodology is based on a two-stage module. The initial frequency source is provided by a high frequency Gunn diode and is the main focus of this work. The output from this diode is then coupled into a multiplier module. The multiplier provides higher frequencies by the generation of harmonics of the input signal by means of a non-linear element, such as Schottky diode Varactor. A realistic Schottky diode model developed in SILVACOTM is presented in this work.This thesis describes the work done to develop predictive models for Gunn Diode devices using SILVACOTM. These physically-based simulations provide the opportunity to increase understanding of the effects of changes to the device's physical structure, theoretical concepts and its general operation. Thorough understanding of device physics was achieved to develop a reliable Gunn diode model. The model development included device physical structure building, material properties specification, physical models definition and using appropriate biasing conditions.The initial goal of the work was to develop a 2D model for a Gunn diode commercially manufactured by e2v Technologies Plc. for use in second harmonic mode 77GHz Intelligent Adaptive Cruise Control (ACC) systems for automobiles. This particular device was chosen as its operation is well understood and a wealth of data is available for validation of the developed physical model. The comparisons of modelled device results with measured results of a manufactured device are discussed in detail. Both the modelled and measured devices yielded similar I-V characteristics and so validated the choice of the physical models selected for the simulations. During the course of this research 2D, 3D rectangular, 3D cylindrical and cylindrical modelled device structures were developed and compared to measured results.The injector doping spike concentration was varied to study its influence on the electric field in the transit region, and was compared with published and measured data.Simulated DC characteristics were also compared with measured results for higher frequency devices. The devices mostly correspond to material previously grown for experimental studies in the development of D-band GaAs Gunn devices. Ambient temperature variations were also included in both simulated and measured data.Transient solutions were used to obtain a time dependent response such as determining the device oscillating frequency under biased condition. These solutions provided modelled device time-domain responses. The time-domain simulations of higher frequency devices which were developed used modelling measured approach are discussed. The studied devices include 77GHz (2nd harmonic), 125 GHz (2nd harmonic) and 100 GHz fundamental devices.During the course of this research, twelve research papers were disseminated. The results obtained have proved that the modelling techniques used, have provided predictive models for novel Transferred Electron Devices (TEDs) operating above 100GHz.

The project contains adventurous research, with an aim to understand and design a planar Gunn diode with a novel integrated circuit configuration to extract the 2nd harmonic. This will potentially enhance the Gunn diode as a high frequency source towards frequencies in excess of 600 GHz. The RF performance from the above integrated circuit was achieved by design and simulation of radial and diamond stub resonators, which were used to short the fundamental oscillation frequency while allowing the second harmonic frequency to pass through to the load. The diamond stub resonator is a new configuration offering a number of advantages which include a higher loaded quality factor and occupies 55% less chip area than a comparable radial stub resonator. The designed novel circuits with integrated planar Gunn diode were fabricated using microwave monolithic integrated circuits (MMIC) technology at the James Watt Nanofabrication centre in Glasgow University. Full DC and microwave characterisation of the diodes and integrated circuits with diodes was carried out using a semiconductor analyser, network analyser (10 MHz to 110GHz) and spectrum analyser (10 MHz to 125GHz). The microwave measurements were carried out at the high frequency RF laboratories in Glasgow University. Both GaAs and InP based Gunn diodes were characterised and RF characterisation work showed that higher fundamental frequencies could be obtained from Gunn diodes fabricated on InGaAs on a lattice matched InP substrate. Planar Gunn diodes with an anode to cathode spacing of 4 microns giving a fundamental frequency of oscillation of 60 GHz were fabricated as an integrated circuit with coplanar waveguide (CPW) circuit elements to extract the second harmonic. A second harmonic frequency of 120 GHz with an RF output power of -14.11 dBm was extracted with very good fundamental frequency suppression. To the authors knowledge this was the first time second harmonic frequencies have been extracted from a planar Gunn diode technology. Aluminium gallium arsenide (AlGaAs) planar Gunn diodes were also designed with an integrated series inductor to match the diode at the fundamental frequency to obtain higher RF output powers. Devices with a 1 micron anode to cathode separation gave the highest fundamental oscillation frequency of 121 GHz the highest reported for a GaAs based Gunn diode and with an RF output power of -9 dBm. These circuits will have potential applications in secure communications, terahertz imaging etc.

This thesis reassesses American AIDS literature of the 1980s and 1990s by focusing on four major writers: the poets Thom Gunn (1929-2004), James Merrill (1926-1995) and Mark Doty (1953-), and the novelist Michael Cunningham (1952-). It questions the dominant critical discourse on literature of the epidemic, contending that while competing versions of the postmodern provided useful models for reading AIDS in the 1980s and 1990s, it is now necessary to adjust the critical position in line with the intellectual turn away from the cultural theories of that time. The introduction provides an overview of the most prevalent constructions of AIDS’ postmodernity through the period, arguing that critics were anxious to fit the epidemic to the theoretical models of the day, and going on to suggest that the writers under scrutiny actively question or even resist these models. Chapter One reads the later collections of Thom Gunn against his earlier work, arguing that he writes a "poetry of prophylaxis" which draws on his literary past in order to construct a defence against the uncertainties of the epidemic age. Chapter Two develops this question of self-reconstruction, examining the last two collections of James Merrill and his 1993 memoir in light of his own diagnosis with HIV. It proposes that in the renegotiation of his body, he might help the reader both remember and "re-member" him. Chapter Three turns to the work of Mark Doty, in particular the memoir Heaven’s Coast and the two collections, My Alexandria (1995) and Atlantis (1996), suggesting that Doty reclaims metaphor for palliative good at a time when AIDS theorists such as Paula Treichler registered scepticism during the "epidemic of signification". Chapter Four discusses the 1990s novels of Michael Cunningham, arguing that in order to “know” AIDS, outside of contemporaneous postmodern readings, it is necessary to "re-know" or "recognise" older literary models. The thesis ends with a brief account of post-1990s AIDS literature and theory, before concluding that each writer argues for models of literary continuity as a means of neutralising the possible creative rupture wrought by immunodeficiency.

La découverte en 1963 par J.B. GUNN d'instabilités électroniques dans des échantillons d'arséniure de gallium a permis la réalisation d'oscillateurs solides dans la gamme des ondes centimétriques et millimétriques. Ces oscillateurs possèdent plusieurs avantages sur les anciens générateurs hyperfréquences à tubes, klystrons par exemple : alimentation simplifiée, stabilité en fréquence accrue, large bande de fréquence de fonctionnement, coûts de fabrication réduits. Après un rappel sur la théorie de l'effet Gunn, cette thèse présente l'étude de quelques applications de ces oscillateurs, mettant en particulier l'accent sur leur stabilité en fréquence. C'est ainsi qu'il est décrit un montage permettant le battement en fréquence de deux oscillateurs, puis un autre permettant l'asservissement en fréquence d'un oscillateur à une longueur de guide d'onde. Ce dernier montage est ensuite utilisé pour mesurer la permittivité de différents gaz introduits dans le guide d'onde. Les résultats obtenus sont comparés à des mesures antérieures effectuées par d'autres moyens.

This thesis presents the design and implementation of a millimeter-wave Gunn diode oscillator operating at 35 GHz (Ka (R) 26.5-40 GHz Band). The aim of the study is to produce a high frequency, high power signal from a negative resistance device situated in a waveguide cavity by applying a direct current bias. First the physics of Gunn diodes is studied and the requirements that Gunn diode operates within the negative differential resistance region is obtained. Then the best design configuration is selected. The design of the oscillator includes the design of the waveguide housing, diode mounting and the bias insertion network. Some simulation tools are used to predict, approximately, the behaviour of the oscillator and the bias coupling circuit. For tuning purposes, a sliding backshort and a triplescrew- tuner system is used. For different bias values and different positions of the tuning elements oscillations are observed. A much more stable and higher magnitude oscillations were obtained with the inclusion of &ldquo / resonant disc&rdquo / placed on top of the diode. 15 dBm power was measured at a frequency of 28 GHz. Laboratory measurements have been carried out to determine the oscillator frequency, power output and stability for different bias conditions.

Study of pseudotachylytes (PT) (frictional melts) can provide information on the physical and chemical conditions at the earthquake source. This study examines the influence of asperityscale fault dynamics on asperity temperature distribution, and therefore, the potential for frictional melting to occur. Frictional melting occurs adiabatically, and is initiated between opposing asperity tips during fault slip. Our model considers 2-D heat conduction in elastic, isotropic, hemispherical asperities, with temperature dependent thermal properties. The only heat source is a point heat flux pulse at the asperity tip. The non-linear problem was solved using the -form of Newton-Kantorovich procedure coupled with the -form of Douglas-Gunn two level finite difference scheme, while the linear problem required only the latter method. Results for quartz and feldspar indicate that peak temperatures can reach melting point values for typical asperity sizes (1-100 mm), provided that contact (frictional) shear stress is sufficiently high. For any asperity size, the temperature distribution peak becomes insignificant by the time it reaches the asperity center. These results imply that much of asperity scale melting is highly localized, which may explain why most PT veins in the field are usually very thin. However, in some cases, successive asperity encounters may generate temperature increases large enough to trigger the massive melting inferred from typical PT exposures. Significant differences were observed between the results of the linear and nonlinear models.

Modern high frequency electronic devices are continually becoming smaller in area but capable of generating higher RF power, thereby increasing the dissipated power density. For many microwave devices, for example the planar Gunn diode, standard thermal management may no longer be sufficient to effectively remove the increasing dissipated power. The work has looked at the design and development of an active micro-cooler, which could be fully integrated with the planar Gunn diode at wafer level as a monolithic microwave integrated circuit (MMIC). The work also resulted in the further development of novel thermal measurement techniques, using micro-particle sensors with infra-red (IR) thermal microscopy and for the first time to measure thermal profiles along the channel of the planar Gunn diode. To integrate the gallium arsenide (GaAs) based planar Gunn diode and micro-cooler, it was first necessary to design and fabricate individual GaAs based planar Gunn diodes and micro-coolers for thermal and electrical characterisation. To obtain very small area micro-coolers, superlattice structures were investigated to improve the ratio between the electrical and thermal conductivities of the micro-cooler. To measure the specific contact resistivity of the superlattice based micro-cooler contacts, the Reeves & Harrison TLM (transmission line method) was used as it included both horizontal and vertical components of the contact resistance. It was found, for the GaAs based micro-cooler, only small amounts of cooling (< 0.4 °C) could be obtained, therefore the novel temperature measurement method using micro-particle sensors placed on both the anode and cathode contacts was utilised. The bias probes used to supply DC power to the micro-coolers were found to thermally load these very small structures, which led to anomalously high measured cooling temperatures of > 1°C. A novel approach of determining if the measured cooling temperature was due to cooling or probe loading was developed. A 1D model for the integrated micro-cooler was developed and the results indicated that when the micro-cooler was used as a cooling element in a monolithic microwave integrated circuit, the supporting substrate thickness was very important. Simulation showed to obtain cooling the substrate thickness had to be very thin (< 50 μm), which may preclude the use of GaAs micro-coolers as part of a monolithic microwave integrated circuit.