12,371 research outputs found

    Radiation Measurements and Data Analysis of Turbulent Premixed Lean Flame

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    An accurate understanding of the radiation transfer in turbulent premixed lean flame is critical for improving energy efficiencies and reducing emissions such as nitric oxide and soot. Radiation measurement is an effective and nonintrusive way to study the radiation properties of turbulent premixed lean flames. In this study, a high-speed infrared camera was utilized to measure the planar radiation from turbulent premixed lean flames under different conditions. Time-dependent flame images were acquired and radiation statistics were calculated and compared to investigate the effects of equivalence ratio, heat release rate, hydrogen pilot flame rate, and co-flow rate on the radiation intensity of the flames. Results show that radiation intensity increases with equivalence ratio and heat release rate. However, changes of hydrogen pilot flame rate and co-flow rate have little impact on the radiation intensity. These experimental data are essential for the study of turbulent premixed lean flames and the calibration of the empirical relations in the simulation models

    Quantitative Test of SO(5) Symmetry in the Vortex State of Nd1.85Ce0.15CuO4Nd_{1.85}Ce_{0.15}CuO_4

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    By numerically solving models with competing superconducting and antiferromagnetic orders, we study the magnetic field dependence of the antiferromagnetic moment in both the weak and strong field regimes. Through a omparison with the neutron scattering results of Kang et al and Matsuura et al.on Nd1.85Ce0.15CuO4Nd_{1.85}Ce_{0.15}CuO_4, we conclude that this system is close to a SO(5) symmetric critical point. We also make a quantitative prediction on increasing the upper critical field Bc2B_{c2} and the superconducting transition temperature TcT_c by applying an in-plane magnetic field.Comment: 4 pages, 3 figures v3: final version PRL 92, 107002 (2004

    Self-consistency of optimizing finite-time Carnot engines with the low-dissipation model

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    The efficiency at the maximum power (EMP) for finite-time Carnot engines established with the low-dissipation model, relies significantly on the assumption of the inverse proportion scaling of the irreversible entropy generation ΔS(ir)\Delta S^{(\mathrm{ir})} on the operation time τ\tau, i.e., ΔS(ir)1/τ\Delta S^{(\mathrm{ir})}\propto1/\tau. The optimal operation time of the finite-time isothermal process for EMP has to be within the valid regime of the inverse proportion scaling. Yet, such consistency was not tested due to the unknown coefficient of the 1/τ1/\tau-scaling. In this paper, using a two-level atomic heat engine as an illustration, we reveal that the optimization of the finite-time Carnot engines with the low-dissipation model is self-consistent only in the regime of ηC1\eta_{\mathrm{C}}\ll1, where ηC\eta_{\mathrm{C}} is the Carnot efficiency. In the large-ηC\eta_{\mathrm{C}} regime, the operation time for EMP obtained with the low-dissipation model is not within the valid regime of the 1/τ1/\tau-scaling, and the exact EMP is found to surpass the well-known bound η+=ηC/(2ηC)\eta_{+}=\eta_{\mathrm{C}}/(2-\eta_{\mathrm{C}})Comment: 6 pages, 4 figures, Comments are welcom

    A Second Method to Photometrically Align Multi-Site Microlensing Light Curves: Source Color in Planetary Event MOA-2007-BLG-192

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    At present, microlensing light curves from different telescopes and filters are photometrically aligned by fitting them to a common model. We present a second method based on photometry of common field stars. If two spectral responses are similar (or the color of the source is known) then this technique can resolve important ambiguities that frequently arise when predicting the future course of the event, and that occasionally persist even when the event is over. Or if the spectral responses are different, it can be used to derive the color of the source when that is unknown. We present the essential elements of this technique and apply it to the case of MOA-2007-BLG-192, an important planetary event for which the system may be a terrestrial planet orbiting a brown dwarf or very low mass star. The refined estimate of the source color that we derive here, V-I=2.36 +- 0.03, will aid in making the estimate of the lens mass more precise.Comment: 16 pages including 3 figures. Submitted to Ap

    Pb Neurotoxicity: Neuropsychological Effects of Lead Toxicity

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    Neurotoxicity is a term used to describe neurophysiological changes caused by exposure to toxic agents. Such exposure can result in neurocognitive symptoms and/or psychiatric disturbances. Common toxic agents include heavy metals, drugs, organophosphates, bacterial, and animal neurotoxins. Among heavy metal exposures, lead exposure is one of the most common exposures that can lead to significant neuropsychological and functional decline in humans. In this review, neurotoxic lead exposure\u27s pathophysiology, etiology, and epidemiology are explored. In addition, commonly associated neuropsychological difficulties in intelligence, memory, executive functioning, attention, processing speed, language, visuospatial skills, motor skills, and affect/mood are explored

    Signature of Spin Collective Mode in Local Tunneling Spectra of a d-wave Superconductor

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    We consider the influence of magnetic excitations on the local density of states in the d-wave superconductor. The magnetic susceptibility is calculated within the renormalized ttJt-t'-J model and its influence on the quasiparticle self-energy is considered using a minimal model originally proposed by Polkovnikov {\it et al.}[cond-mat/0203176]. We find the local density of states possess periodic components both along (π,0)(\pi,0) and (π,π)(\pi,\pi) directions with the associated wavevectors changing in magnitude as the quasiparticle energy is varied. Comparison with the STM experiment reveals that the calculated LDOS modulation is inconsistent with the measured data.Comment: Two figures separately attached as .jpg file
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