11 resultados para propagating in the slant path

em Aston University Research Archive


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The paper argues that the current emerging international development policies of the Visegrád (V4) countries are heavily influenced by the certain aspects of the Communist past and the transition process. Due to these influences, the V4 countries have difficulties in adapting the foreign aid practices of Western donors and this leads to the emergence of a unique Central and Eastern European development cooperation model. As an analytical background, the paper builds on the path dependency theory of transition. A certain degree of path dependence is clearly visible in V4 foreign aid policies, and the paper analyses some aspects of this phenomenon: how these new emerging foreign aid donors select their partner countries, how much they spend on aid, how they formulate their aid delivery policies and institutions and what role the non-state actors play. The main conclusions of the paper are that the legacies of the Communist past have a clear influence and the V4 countries still have a long way to go in adapting their aid policies to international requirements.

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The baleful legacy of the wars of the 1990s continues to dog the states and societies of the former Yugoslavia and has overshadowed the disappointingly slow and hesitant trajectory of the region towards the EU. At the start of the new millennium, with the removal of key wartime leaders from the political scene in both Croatia and Serbia, it was widely hoped that the region would prove able to ‘leave the past behind’ and rapidly move on to the hopeful new agenda of EU integration. The EU’s Copenhagen criteria, which in 1993 first explicitly set out the basic political conditions expected of aspirant EU Member States, proved effective in the case of the new democracies of Central and Eastern Europe in supporting the entrenchment of democratic norms and practices, and stimulating reconciliation and good neighbourly relations among countries with turbulent histories. Building on this experience, the Stabilisation and Association Process, launched for the countries of the Western Balkans in 1999, included both full cooperation with the International Criminal Tribunal for the former Yugoslavia (ICTY) and regional reconciliation among the political conditions set for advancing these countries on the path to EU integration. EU political conditionality was intended to support the efforts of new political leaders to redefine national goals away from the nationalist enmities of the past and focus firmly on forging a path to a better future. This Chaillot Paper examines the extent to which this strategy has worked, especially in the light of the difficulties it has encountered in the face of strong resistance to cooperation among sections of the former Yugoslav population, many of whom have not yet fully acknowledged the crimes committed during the 1990s. Key chapters in the volume raise the vital questions of leadership and political will. EU political conditionality does not work unless the EU has a partner ready and willing to ‘play the game’, which presupposes that EU integration has become the overriding priority on the national political agenda.

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This research aimed to provide a comparative analysis of South Asian and White British students in their academic attainment at school and university and in their search for employment. Data were gathered by using a variety of methodological techniques. Completed postal questionnaires were received from 301 South Asian and White British undergraduates from 12 British universities, who were in their final year of study in 1985. In depth interviews were also conducted with 49 graduates who were a self selected group from the original sample. Additional information was also collected by using diary report forms and by administering a second postal questionnaire to selected South Asian and White British participants. It was found that while the pre-university qualifications of the White British and South Asian undergraduates did not differ considerably, many members in the latter group had travelled a more arduous path to academic success. For some South Asians, school experiences included the confrontation of racist attitudes and behaviour, both from teachers and peers. The South Asian respondents in this study were more likely than their White British counterparts, to have attempted some C.S.E. examinations, obtained some of their `O' levels in the Sixth Form and retaken their `A' levels. As a result the South Asians were on average older than their White British peers when entering university. A small sample of South Asians also found that the effects of racism were perpetuated in higher education where they faced difficulty both academically and socially. Overall, however, since going to university most South Asians felt further drawn towards their `cultural background', this often being their own unique view of `Asianess'. Regarding their plans after graduation, it was found that South Asians were more likely to opt for further study, believing that they needed to be better qualified than their White British counterparts. For those South Asians who were searching for work, it was noted that they were better qualified, willing to accept a lower minimum salary, had made more job applications and had started searching for work earlier than the comparable White British participants. Also, although generally they were not having difficulty in obtaining interviews, South Asian applicants were less likely to receive an offer of employment. In the final analysis examining their future plans, it was found that a large proportion of South Asian graduates were aspiring towards self employment.

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Visual perception is dependent on both light transmission through the eye and neuronal conduction through the visual pathway. Advances in clinical diagnostics and treatment modalities over recent years have increased the opportunities to improve the optical path and retinal image quality. Higher order aberrations and retinal straylight are two major factors that influence light transmission through the eye and ultimately, visual outcome. Recent technological advancements have brought these important factors into the clinical domain, however the potential applications of these tools and considerations regarding interpretation of data are much underestimated. The purpose of this thesis was to validate and optimise wavefront analysers and a new clinical tool for the objective evaluation of intraocular scatter. The application of these methods in a clinical setting involving a range of conditions was also explored. The work was divided into two principal sections: 1. Wavefront Aberrometry: optimisation, validation and clinical application The main findings of this work were: • Observer manipulation of the aberrometer increases variability by a factor of 3. • Ocular misalignment can profoundly affect reliability, notably for off-axis aberrations. • Aberrations measured with wavefront analysers using different principles are not interchangeable, with poor relationships and significant differences between values. • Instrument myopia of around 0.30D is induced when performing wavefront analysis in non-cyclopleged eyes; values can be as high as 3D, being higher as the baseline level of myopia decreases. Associated accommodation changes may result in relevant changes to the aberration profile, particularly with respect to spherical aberration. • Young adult healthy Caucasian eyes have significantly more spherical aberration than Asian eyes when matched for age, gender, axial length and refractive error. Axial length is significantly correlated with most components of the aberration profile. 2. Intraocular light scatter: Evaluation of subjective measures and validation and application of a new objective method utilising clinically derived wavefront patterns. The main findings of this work were: • Subjective measures of clinical straylight are highly repeatable. Three measurements are suggested as the optimum number for increased reliability. • Significant differences in straylight values were found for contact lenses designed for contrast enhancement compared to clear lenses of the same design and material specifications. Specifically, grey/green tints induced significantly higher values of retinal straylight. • Wavefront patterns from a commercial Hartmann-Shack device can be used to obtain objective measures of scatter and are well correlated with subjective straylight values. • Perceived retinal stray light was similar in groups of patients implanted with monofocal and multi focal intraocular lenses. Correlation between objective and subjective measurements of scatter is poor, possibly due to different illumination conditions between the testing procedures, or a neural component which may alter with age. Careful acquisition results in highly reproducible in vivo measures of higher order aberrations; however, data from different devices are not interchangeable which brings the accuracy of measurement into question. Objective measures of intraocular straylight can be derived from clinical aberrometry and may be of great diagnostic and management importance in the future.

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This research developed, proposed and tested an integrated psychological process to performance model. The model utilized the overarching theory of social exchange to incorporate the climate perceptions and affective reactions of 3,012 employees across 88 UK call centres. In the pursuit of parsimony, a review of the applied psychology literature gave rise to a model where the path between global service climate and contextual performance was fully mediated by, first, perceived organizational support, second, job satisfaction and third, affective commitment. The resulting integrated and parsimonious model was tested via SEM and the mediation hypotheses were tested via a series of nested competing models. A moderate fit and partial, rather than full, mediation were reported. Nested Competing Model 4 proved to be the most parsimonious and to have the best fit. It is important to recognise, however, that Nested Competing Model 4 is not intended to be the most comprehensive model (which would include all significant paths), but a more practically useful one (i.e. parsimonious), that focuses on the main relationships.

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In this paper, we propose a saturable absorber (SA) device consisting on an in-fiber micro-slot inscribed by femtosecond laser micro fabrication, filled by a dispersion of Carbon Nanotubes (CNT). Due to the flexibility of the fabrication method, efficient and simple integration of the mode-locking device directly into the optical fiber is achieved. Furthermore, the fabrication process offers a high level of control over the dimensions and location of the micro-slots. We apply this fabrication flexibility to extend the interaction length between the CNT and the propagating optical field along the optical fiber, hence enhancing the nonlinearity of the device. Furthermore, the method allows the fabrication of devices that operate by either a direct field interaction (when the central peak of the propagating optical mode passes through the nonlinear media) or an evanescent field interaction (only a fraction of the optical mode interacts with the CNT). In this paper, several devices with different interaction lengths and interaction regimes are investigated. Self-starting passively modelocked laser operation with an enhanced nonlinear interaction is observed using CNT-based SAs in both interaction regimes. This method constitutes a simple and suitable approach to integrate the CNT into the optical system as well as enhancing the optical nonlinearity of CNT-based photonic devices.

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Fatigue crack growth in high strength aluminium alloy 7150 commercial plate material has been studied in both laboratory air and acidified aqueous salt solution. The aggressive aqueous environment enhanced fatigue crack growth rates by up to an order in magnitude compared to laboratory air. The enhancement in fatigue crack growth rate was accompanied by evidence of embrittlement in the crack path, involving both brittle intergranular and transgranular failure modes. Both the enhancement of fatigue crack growth rates and the extent of intergranular growth modes are dependent on cyclic frequency which, along with the absence of a similar frequency effect in a spray-formed version of the material with a significantly different grain structure, supports a mechanism of grain boundary hydrogen diffusion for intergranular corrosion fatigue crack growth. The convergence of corrosion fatigue crack growth rates at high ΔK in both spray-formed and conventional plate materials coincides with the operation of identical transgranular corrosion fatigue modes dependent on strain-controlled hydrogen diffusion ahead of the crack tip. © 1997 Acta Metallurgica Inc.

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This article employs nonlinear smooth transition models to analyze the relationship between upstream and midstream prices of petroleum products. We test for the presence of nonlinearities in price linkages using both weekly series constructed using official EU procedures and also daily industry series applied for the first time. Our results show that the estimated shape of the transition function and equilibrium reversion path depend on the frequency of the price dataset. Our analysis of the crude oil to wholesale price transmission provides evidence of nonlinearities when prices are observed with daily frequency. The nature of the nonlinearities provides evidence in support of the existence of menu costs or, more generally, frictions in the markets rather than supply adjustment costs. This result differs from that found for the U.S. petroleum markets. © 2012 American Statistical Association.

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Background: Electrosurgery units are widely employed in modern surgery. Advances in technology have enhanced the safety of these devices, nevertheless, accidental burns are still regularly reported. This study focuses on possible causes of sacral burns as complication of the use of electrosurgery. Burns are caused by local densifications of the current, but the actual pathway of current within patient's body is unknown. Numerical electromagnetic analysis can help in understanding the issue. Methods: To this aim, an accurate heterogeneous model of human body (including seventy-seven different tissues), electrosurgery electrodes, operating table and mattress was build to resemble a typical surgery condition. The patient lays supine on the mattress with the active electrode placed onto the thorax and the return electrode on his back. Common operating frequencies of electrosurgery units were considered. Finite Difference Time Domain electromagnetic analysis was carried out to compute the spatial distribution of current density within the patient's body. A differential analysis by changing the electrical properties of the operating table from a conductor to an insulator was also performed. Results: Results revealed that distributed capacitive coupling between patient body and the conductive operating table offers an alternative path to the electrosurgery current. The patient's anatomy, the positioning and the different electromagnetic properties of tissues promote a densification of the current at the head and sacral region. In particular, high values of current density were located behind the sacral bone and beneath the skin. This did not occur in the case of non-conductive operating table. Conclusion: Results of the simulation highlight the role played from capacitive couplings between the return electrode and the conductive operating table. The concentration of current density may result in an undesired rise in temperature, originating burns in body region far from the electrodes. This outcome is concordant with the type of surgery-related sacral burns reported in literature. Such burns cannot be immediately detected after surgery, but appear later and can be confused with bedsores. In addition, the dosimetric analysis suggests that reducing the capacity coupling between the return electrode and the operating table can decrease or avoid this problem. © 2013 Bifulco et al.; licensee BioMed Central Ltd.

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eHabitat is a Web Processing Service (WPS) designed to compute the likelihood of finding ecosystems with equal properties. Inputs to the WPS, typically thematic geospatial "layers", can be discovered using standardised catalogues, and the outputs tailored to specific end user needs. Because these layers can range from geophysical data captured through remote sensing to socio-economical indicators, eHabitat is exposed to a broad range of different types and levels of uncertainties. Potentially chained to other services to perform ecological forecasting, for example, eHabitat would be an additional component further propagating uncertainties from a potentially long chain of model services. This integration of complex resources increases the challenges in dealing with uncertainty. For such a system, as envisaged by initiatives such as the "Model Web" from the Group on Earth Observations, to be used for policy or decision making, users must be provided with information on the quality of the outputs since all system components will be subject to uncertainty. UncertWeb will create the Uncertainty-Enabled Model Web by promoting interoperability between data and models with quantified uncertainty, building on existing open, international standards. It is the objective of this paper to illustrate a few key ideas behind UncertWeb using eHabitat to discuss the main types of uncertainties the WPS has to deal with and to present the benefits of the use of the UncertWeb framework.

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We investigate the theoretical and numerical computation of rare transitions in simple geophysical turbulent models. We consider the barotropic quasi-geostrophic and two-dimensional Navier–Stokes equations in regimes where bistability between two coexisting large-scale attractors exist. By means of large deviations and instanton theory with the use of an Onsager–Machlup path integral formalism for the transition probability, we show how one can directly compute the most probable transition path between two coexisting attractors analytically in an equilibrium (Langevin) framework and numerically otherWe adapt a class of numerical optimization algorithms known as minimum action methods to simple geophysical turbulent models. We show that by numerically minimizing an appropriate action functional in a large deviation limit, one can predict the most likely transition path for a rare transition between two states. By considering examples where theoretical predictions can be made, we show that the minimum action method successfully predicts the most likely transition path. Finally, we discuss the application and extension of such numerical optimization schemes to the computation of rare transitions observed in direct numerical simulations and experiments and to other, more complex, turbulent systems.