Asymptotic Behavior of Strategies in the Repeated Prisoner's Dilemma Game in the Presence of Errors

We examine the asymptotic behavior of a finite, but error-prone population, whose agents can choose one of ALLD (always defect), ALLC (always cooperate), or Pavlov (repeats the previous action if the opponent cooperated and changes action otherwise) to play the repeated Prisoner's Dilemma. A novelty of the study is that it allows for three types of errors that affect agents' strategies in distinct ways: (a) implementation errors, (b) perception errors of one's own action, and (c) perception errors of the opponent's action. We also derive numerical results based on the payoff matrix used in the tournaments of Axelrod (1984). Strategies' payoffs are monitored as the likelihood of committing errors increases from zero to one, which enables us to provide a taxonomy of best response strategies. We find that for some range of error levels, a unique best response (i.e. a dominant strategy) exists. In all other, the population composition can vary based on the proportion of each strategist's type and/or the payoffs of the matrix. Overall, our results indicate that the emergence of cooperation is considerably weak at most error levels

Development of solid state thick film zirconia oxygen gas sensors.

Aspects relating to and including the development of thick film amperometric zirconia oxygen sensors were investigated. These devices, which were operated in the range 550-950°C, had a laminated structure in which a cathode, an electrolyte and an anode were printed, in that order, onto a planar alumina substrate. The anode and electrolyte were porous and during sensor Operation also acted as a diffusion barrier, restricting the rate of oxygen diffusion to the cathode. A thick film platinum heater was also developed to maintain the sensor at its operating temperature while acting simultaneously as a résistance thermometer; it was screen-printed onto the substrate on the reverse side to the sensor. The individual components were characterised and optimised prior to assembly of complete sensors. Zirconia films were deposited by screen-printing onto alumina substrates. Careful attention was paid to formulation of zirconia inks, drying and firing procedures. Temperatures above 1350°C were necessary to sinter the zirconia to a low (<0.1%) though not zero porosity. The high sintering temperatures were found to result in the diffusion of impurities from the 96% alumina Substrate into the zirconia film which accelerated grain growth. X-ray diffraction showed that the grain growth resulted in transformation of the metastable tetragonal zirconia to the monoclinic form: where this occurred frequency response analysis of the films showed the expected decrease in ionic conductivity. These effects were absent on high purity (99.6%) alumina substrates. Platinum-zirconia cermets were investigated as possible electrodes. When screen-printed and fired at 1000°C for 1 hour and operated in the range 500-700°C, electrode activity was orders of magnitude greater than for pure porous platinum electrodes and increased substantially with increasing zirconia fractions provided electronic continuity was maintained within the film. High firing temperatures (> 1000°C), which were necessary for preparing a sensor with co-fired electrolyte and electrodes, decreased electrode activities although cermets remained greatly superior to pure platinum. Planar amperometric zirconia oxygen sensors were prepared using thick-film technology exclusively. When a voltage (0.5-1.4 V) was applied between the electrodes, a current flowed which was directly proportional to the oxygen concentration in the range up to 21%; this has not previously been achieved with such sensors. Characteristics were shown to be dependent upon firing temperature and substrate purity. Interestingly, temperature coefficients of the output were positive and negative for sensors fired at temperatures up to 1400 and above 1450°C respectively. Operation in the combustion products of a gas-burning flue demonstrated linear dependence upon calculated oxygen concentration. Heaters, printed using either fritted or unfritted platinum inks, were given extended treatments in a furnace at elevated temperatures (1000-1300°C) to accelerate ageing effects. Measurements were made of résistance (at 20°C), platinum evaporation rate and film cross-sectional area and these were correlated with the microstructure. The variation of résistance (at 20°C) of the films was analysed using effective medium theory invoked in order to quantify the blocking effect of the non-metallic fractions. During the initial phase (résistance decreasing) the governing factor was probably the high resistance of necks between contacting platinum particles. During the subsequent phase (resistance increasing) the resistance was controlled principally by the formation and growth of voids

Existential time-limited therapy: an interpretative phenomenological analysis of the experience of existential counselling psychologists and psychotherapists providing therapy in time-limited contexts

This dissertation explores the experience of existential counselling psychologists and psychotherapists providing time-limited therapy. Ten participants were interviewed, using semi-structured interviews, focusing on the emotions, meaning-making processes and attitudes that constitute their experience. The material was analysed using Interpretative Phenomenological Analysis - IPA. Five superordinate themes were identified, highlighting the main constituents of the experience of existential therapists in time-limited settings: the experience of time-limitation, the experience of ending, the experience of the therapeutic process, attitudes towards time-limited therapy and support systems. Existing literature on time-limited therapy and the existential approach was utilised to shed light on the results and to reach a better understanding of the implications that this study has on the existential approach, supervisory and training settings, and counselling psychology. It is suggested that existential time-limited therapy is particularly relevant for the widespread provision of time-limited therapies, and its application is based on three main values: the philosophical value, the relational value and the holistic value. The importance of support systems for therapists providing existential time-limited therapy, in the form of supervision and training, was also highlighted, with reference to the particular challenges and opportunities that such a work entails. Finally, the contribution of this study to the division of Counselling Psychology, and the necessity for such a research in order to safeguard the division’s values, promote its pluralistic identity, and provide ethical and competent services to those in need, is also presented

Review of presentations at the 6th European Lupus Meeting 3-5 March 2005.

The 6th European Lupus Meeting was held at the Royal College of Physicians of London and was attended by 450 delegates. The conference brought together leading speakers from Europe and North America who reviewed current knowledge and exciting new developments in both clinical and basic science aspects of systemic lupus erythematosus. This review summarizes the major points covered in each session

High throughput spatial convolution filters on FPGAs

Digital signal processing (DSP) on field- programmable gate arrays (FPGAs) has long been appealing because of the inherent parallelism in these computations that can be easily exploited to accelerate such algorithms. FPGAs have evolved significantly to further enhance the mapping of these algorithms, included additional hard blocks, such as the DSP blocks found in modern FPGAs. Although these DSP blocks can offer more efficient mapping of DSP computations, they are primarily designed for 1-D filter structures. We present a study on spatial convolutional filter implementations on FPGAs, optimizing around the structure of the DSP blocks to offer high throughput while maintaining the coefficient flexibility that other published architectures usually sacrifice. We show that it is possible to implement large filters for large 4K resolution image frames at frame rates of 30–60 FPS, while maintaining functional flexibility