The role of coherent structures in the generation of noise for subsonic jets

Acoustic measurements were made in the 'near' (r/D 60, x/D 60) field for high Reynolds number (184,000 to 262,000) axisymmetric cold air jets exhausting at atmospheric pressure. These measurements were in conjunction with an investigation which characterized the large scale coherent structure in the flow field of Mach number 0.6 to 0.8 jets. Natural jets as well as artificially excited jets were studied. Directivity plots were made for both natural jets and jets excited at various frequencies. Overall noise radiated by the jets reached a maximum value around 30 deg from the jet axis. However, individual frequencies emitted maximum sound pressure level at different angles from the jet axis. As the angle from the jet axis increased, the spectra of the noise shifted to higher frequencies

Help seeking for cancer 'alarm' symptoms: a qualitative interview study of primary care patients in the UK.

Delay in help seeking for cancer 'alarm' symptoms has been identified as a contributor to delayed diagnosis

Shakespeare the Elizabethan

Paper by Virgil K. Whitake

Faith and Disbelief

Is faith that p compatible with disbelief that p? I argue that it is. After surveying some recent literature on the compatibility of propositional (so-called faith-that) and non-propositional (faith-in) forms of faith with the lack of belief, I take the next step and offer several arguments for the thesis that both these forms of faith are also compatible, in certain cases, with outright disbelief. This is contrary to the views of some significant recent commentators on propositional faith, including Robert Audi and Daniel Howard-Snyder. The primary argument revolves around the possibility of maintaining a single faith through drastic changes in cognitive attitude. I argue that once we allow that propositional faith is compatible with weaker cognitive attitudes than belief, such as acceptance or assent, there is prima facie reason to consider propositional faith as sometimes compatible with disbelief. I then consider objections and offer some final reflections on the significance of the thesis

Spherical collapse model in agegraphic dark energy cosmologies

Under the commonly used spherical collapse model, we study how dark energy affects the growth of large scale structures of the Universe in the context of agegraphic dark energy models. The dynamics of the spherical collapse of dark matter halos in nonlinear regimes is determined by the properties of the dark energy model. We show that the main parameters of the spherical collapse model are directly affected by the evolution of dark energy in the agegraphic dark energy models. We compute the spherical collapse quantities for different values of agegraphic model parameter $\alpha$ in two different scenarios: first, when dark energy does not exhibit fluctuations on cluster scales, and second, when dark energy inside the overdense region collapses similar to dark matter. Using the Sheth-Tormen and Reed mass functions, we investigate the abundance of dark matter halos in the framework of agegraphic dark energy cosmologies. The model parameter $\alpha$ is a crucial parameter in order to count the abundance of dark matter halos. Specifically, the present analysis suggests that the agegraphic dark energy model with bigger (smaller) value of $\alpha$ predicts less (more) virialized halos with respect to that of $\Lambda$CDM cosmology. We also show that in agegraphic dark energy models, the number of halos strongly depends on clustered or uniformed distributions of dark energy.Comment: 14 pages, 7 figures. Accepted in Physical Review

Design of thrust vectoring exhaust nozzles for real-time applications using neural networks

Thrust vectoring continues to be an important issue in military aircraft system designs. A recently developed concept of vectoring aircraft thrust makes use of flexible exhaust nozzles. Subtle modifications in the nozzle wall contours produce a non-uniform flow field containing a complex pattern of shock and expansion waves. The end result, due to the asymmetric velocity and pressure distributions, is vectored thrust. Specification of the nozzle contours required for a desired thrust vector angle (an inverse design problem) has been achieved with genetic algorithms. This approach is computationally intensive and prevents the nozzles from being designed in real-time, which is necessary for an operational aircraft system. An investigation was conducted into using genetic algorithms to train a neural network in an attempt to obtain, in real-time, two-dimensional nozzle contours. Results show that genetic algorithm trained neural networks provide a viable, real-time alternative for designing thrust vectoring nozzles contours. Thrust vector angles up to 20 deg were obtained within an average error of 0.0914 deg. The error surfaces encountered were highly degenerate and thus the robustness of genetic algorithms was well suited for minimizing global errors

Capturing the time-varying drivers of an epidemic using stochastic dynamical systems

Epidemics are often modelled using non-linear dynamical systems observed through partial and noisy data. In this paper, we consider stochastic extensions in order to capture unknown influences (changing behaviors, public interventions, seasonal effects etc). These models assign diffusion processes to the time-varying parameters, and our inferential procedure is based on a suitably adjusted adaptive particle MCMC algorithm. The performance of the proposed computational methods is validated on simulated data and the adopted model is applied to the 2009 H1N1 pandemic in England. In addition to estimating the effective contact rate trajectories, the methodology is applied in real time to provide evidence in related public health decisions. Diffusion driven SEIR-type models with age structure are also introduced.Comment: 21 pages, 5 figure

Atomic oxygen effects on LDEF experiment AO171

The Solar Array Materials Passive Long Duration Exposure Facility (LDEF) Experiment (SAMPLE), AO171, contained in total approximately 100 materials and materials processes with a 300 specimen complement. With the exception of experiment solar cell and solar cell modules, all test specimens were weighed before flight, thus allowing an accurate determination of mass loss as a result of space exposure. Since almost all of the test specimens were thermal vacuum baked before flight, the mass loss sustained can be attributed principally to atomic oxygen attack. The atomic oxygen effects observed and measured in five classes of materials is documented. The atomic oxygen reactivity values generated for these materials are compared to those values derived for the same materials from exposures on short term shuttle flights. An assessment of the utility of predicting long term atomic oxygen effects from short term exposures is given. This experiment was located on Row 8 position A which allowed all experiment materials to be exposed to an atomic oxygen fluence of 6.93 x 10(exp 21) atoms/cm(sup 2) as a result of being positioned 38 degrees off the RAM direction