40,332 research outputs found

    About the chemical composition of delta Scuti - the prototype of the class of pulsating variables

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    We present chemical abundances in the photosphere of δ\delta Scuti -- the prototype of the class of pulsating variables -- determined from the analysis of a spectrum obtained at Terskol observatory 2 meter telescope with resolution R=52,000R=52,000, signal to noise ratio 250. VLT and IUE spectra were used also . Abundance pattern of \dsct consists of 49 chemical elements. The abundances of Be, P, Ge, Nb, Mo, Ru, Er, Tb, Dy, Tm, Yb, Lu, Hf, Ta, Os, Pt, Th were not investigated previously. The lines of third spectra of Pr and Nd also are investigated for the first time. The abundances of heavy elements show the overabundances with respect to the Sun up to 1 dex. The abundance pattern of \dsct is similar to that of Am-Fm stars.Comment: 8 pages, 2 figures, subm. to Proc. of IAU Symp. 22

    Anxiety and Learning in Dynamic and Static Clock Game Experiments

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    In clock games, agents receive differently-timed private signals when an asset value is above its fundamental. The price crashes to the fundamental when K of N agents have decided to sell. If selling decisions are private, bubbles can be sustained because people delay selling, after receiving signals, knowing that others will delay too. Our results replicate the main features of the one previous experimental study of clock game (in two subject pools): Selling delays are shorter than predicted, but converge toward equilibrium predictions over repeated trials. We also find that delays are shorter in a dynamic game in which selling decisions unfold over time, compared to a static equivalent in which subjects precommit to selling decisions. A model of learning with growing anxiety after signal arrival can reproduce the empirical observations of shorter-than-predicted delay, smaller delay after later signal arrival, and shorter delays in dynamic games

    Analysis of edge impact stresses in composite plates

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    The in-plane edge impact of composite plates, with or without a protection strip, is investigated. A computational analysis based on the Fast Fourier Transform technique is presented. The particular application of the present method is in the understanding of the foreign object damage problem of composite fan blades. The method is completely general and may be applied to the study of other stress wave propagation problems in a half space. Results indicate that for the protective strip to be effective in reducing impact stresses in the composite the thickness must be equal or greater than the impact contact dimension. Large interface shear stresses at the strip - composite boundary can be induced under impact

    An experimental study of coupling between combustor pressure, fuel/air mixing, and the flame

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    Fuel-air mixing behavior under the influence of imposed acoustic oscillations has been studied by investigating the response of the fuel mixture fraction field. The distribution of local fuel mixture fraction inside the mixing zone, which is expected to evolve into the local equivalence ratio in the flame zone, is closely coupled to unstable and oscillatory flame behavior. The Experiment was performed with an aerodynamically-stabilized non-premixed burner. In this study, acoustic oscillations were imposed at 22, 27, 32, 37, and 55Hz. Phase-resolved acetone PLIF was used to image the flow field of both isothermal and reacting flow cases and this data along with the derived quantities of temporal and spatial unmixedness were employed for analysis. The behavior of the unmixedness factor is compared with the previous measurements of oscillations in the flame zone. This comparison shows that local oscillations (of order millimeters or smaller) in fuel/air mixing are closely related to the oscillatory behavior of the flame. For each driving frequency, the mixture fraction oscillates at that frequency but with a slight phase difference between it and the pressure field/flame intensity, indicating that the fuel mixture fraction oscillation are likely the major reason for oscillatory behaviors of this category of flames and combustor geometry

    Hypothetical and Real Choice Differentially Activate Common Valuation Areas

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    Hypothetical reports of intended behavior are commonly used to draw conclusions about real choices. A fundamental question in decision neuroscience is whether the same type of valuation and choice computations are performed in hypothetical and real decisions. We investigated this question using functional magnetic resonance imaging while human subjects made real and hypothetical choices about purchases of consumer goods. We found that activity in common areas of the orbitofrontal cortex and the ventral striatum correlated with behavioral measures of the stimulus value of the goods in both types of decision. Furthermore, we found that activity in these regions was stronger in response to the stimulus value signals in the real choice condition. The findings suggest that the difference between real and hypothetical choice is primarily attributable to variations in the value computations of the medial orbitofrontal cortex and the ventral striatum, and not attributable to the use of different valuation systems, or to the computation of stronger stimulus value signals in the hypothetical condition