228,985 research outputs found

    Welded repairs of punctured thin-walled aluminum pressure vessels

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    Punctures in thin-walled aluminum pressure vessels are repaired by plugging the hole with an interference-fit disc and welding the unit. The repaired vessels withstood test pressures in excess of vessel ultimate design values for 2-, 4-, and 6-inch holes in 0.202-inch-thick aluminum alloy parent material

    Minority Adolescents at Risk for Obesity: Health Behaviors and Perceptions

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    The purpose of this study was to examine behaviors related to nutrition and physical activity of inner-city minority adolescents, and their perception of normal weight and overweight. The research study used a descriptive, non-experimental design which had a convenience sample of thirty-seven 8th grade minority adolescents who attended a chartered urban K-8 grade school in Northern California. There were no statistically significant differences in the results, however, over 50% of the students reported not eating the recommended daily servings of fruits and vegetables. Another 68% reported participating more than 30 minutes in exercising or playing sports during physical education class. Although 42% of the students reported being the right weight, they wanted to lose weight. This demonstrates a need for healthy nutritional behavior and physical activity amongst this population. School nurses can play an important role in identifying at risk students for obesity and provide education in nutrition, structured physical activities, and obesity prevention strategies

    'Requisite irony' and the knowledge based economy: a critical discourse analysis of the drafting of education policy in the european union

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    This chapter makes a case for combining the critical analysis of discourse with an embrace of ‘self-reflexive irony’ (Jessop, 2002, 2004a) in the investigation of the articulations between the Knowledge Based Economy (KBE) and education policy in the European Union (EU). Irony is embraced as a topic within the study of EU governance of education policy in so far as it contributes to an analysis of the activities of supranational and national actors within complex multi-scalar political structures. In addition, the implications of self-reflexive irony are considered so as to suggest a series of clarifications for the process of analysing policy texts within a Critical Discourse Analysis (CDA) framework (Fairclough,1989,1996,1999). In essence, the chapter does two things. It interrogates the contradictory strategies and sources of conflict in the production of EU scale education policy texts and questions both the significance and the stability of the articulation of education reform with KBE discourses. At the same time, the chapter argues that the production of such texts contingently but incrementally contributes to the production of a relatively stable governance framework for EU scale education policy and that it is to the significance of this that a critical discourse analysis leads

    Prospects for Detection of Synchrotron Emission from Secondary Electrons and Positrons in Starless Cores: Application to G0.216+0.016

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    We investigate the diffusion of cosmic rays into molecular cloud complexes. Using the cosmic-ray diffusion formalism of Protheroe, et al. (2008), we examine how cosmic rays diffuse into clouds exhibiting different density structures, including a smoothed step-function, as well as Gaussian and inverse-rr density distributions, which are well known to trace the structure of star-forming regions. These density distributions were modelled as an approximation to the Galactic centre cloud G0.216+0.016, a recently-discovered massive dust clump that exhibits limited signs of massive star formation and thus may be the best region in the Galaxy to observe synchrotron emission from secondary electrons and positrons. Examination of the resulting synchrotron emission, produced by the interaction of cosmic ray protons interacting with ambient molecular matter producing secondary electrons and positrons reveals that, due to projection effects, limb-brightened morphology results in all cases. However, we find that the Gaussian and inverse-rr density distributions show much broader flux density distributions than step-function distributions. Significantly, some of the compact (compared to the 2.2′′2.2'' resolution, 5.3 GHz JVLA observations) sources show non-thermal emission, which may potentially be explained by the density structure and the lack of diffusion of cosmic rays into the cloud. We find that we can match the 5.3 and 20 GHz flux densities of the non-thermal source JVLA~1 and 6 from Rodr\'{\i}guez & Zapata (2014) with a local cosmic ray flux density, a diffusion coefficient suppression factor of χ=0.1−0.01\chi=0.1-0.01 for a coefficient of 3×10273\times10^{27} cm2^2 s−1^{-1}, and a magnetic field strength of 470 μ\muG.Comment: 4 pages, 2 figures, accepted for publication in the Astrophysical Journal Letter

    Pulsar state switching, timing noise and free precession

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    Recent radio pulsar observations have shown that a number of pulsars display interesting long term periodicities in their spin-down rates. At least some of these pulsars also undergo sharp changes in pulse profile. This has been convincingly attributed to the stars abruptly switching between two different magnetospheric states. The sharpness of these transitions has been taken as evidence against free precession as the mechanism behind the long term variations. We argue that such a conclusion is premature. By performing a simple best-fit analysis to the data, we show that the relationship between the observed spin and modulation periods is of approximately the correct form to be accounted for by the free precession of a population of neutron stars with strained crusts, the level of strain being similar in all of the stars, and consistent with the star retaining a memory of a former faster rotation rate. We also provide an argument as to why abrupt magnetospheric changes can occur in precessing stars, and how such changes would serve to magnify the effect of precession in the timing data, making the observation of the precession more likely in those stars where such switching occurs. We describe how future observations could further test the precession hypothesis advanced here.Comment: Additional reference inserted; to appear in MNRA

    A Swiss Pocket Knife for Computability

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    This research is about operational- and complexity-oriented aspects of classical foundations of computability theory. The approach is to re-examine some classical theorems and constructions, but with new criteria for success that are natural from a programming language perspective. Three cornerstones of computability theory are the S-m-ntheorem; Turing's "universal machine"; and Kleene's second recursion theorem. In today's programming language parlance these are respectively partial evaluation, self-interpretation, and reflection. In retrospect it is fascinating that Kleene's 1938 proof is constructive; and in essence builds a self-reproducing program. Computability theory originated in the 1930s, long before the invention of computers and programs. Its emphasis was on delimiting the boundaries of computability. Some milestones include 1936 (Turing), 1938 (Kleene), 1967 (isomorphism of programming languages), 1985 (partial evaluation), 1989 (theory implementation), 1993 (efficient self-interpretation) and 2006 (term register machines). The "Swiss pocket knife" of the title is a programming language that allows efficient computer implementation of all three computability cornerstones, emphasising the third: Kleene's second recursion theorem. We describe experiments with a tree-based computational model aiming for both fast program generation and fast execution of the generated programs.Comment: In Proceedings Festschrift for Dave Schmidt, arXiv:1309.455

    Runoff on rooted trees

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    We introduce an idealised model for overland flow generated by rain falling on a hill-slope. Our prime motivation is to show how the coalescence of runoff streams promotes the total generation of runoff. We show that, for our model, as the rate of rainfall increases in relation to the soil infiltration rate, there is a distinct phase-change. For low rainfall (the subcritical case) only the bottom of the hill-slope contributes to the total overland runoff, while for high rainfall (the supercritical case) the whole slope contributes and the total runoff increases dramatically. We identify the critical point at which the phase-change occurs, and show how it depends on the degree of coalescence. When there is no stream coalescence the critical point occurs when the rainfall rate equals the average infiltration rate, but when we allow coalescence the critical point occurs when the rainfall rate is less than the average infiltration rate, and increasing the amount of coalescence increases the total expected runoff
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