9,370 research outputs found

    Macroeconomic implications of changes in the term premium

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    Linearized New Keynesian models and empirical no-arbitrage macro-finance models offer little insight regarding the implications of changes in bond term premiums for economic activity. We investigate these implications using both a structural model and a reduced-form framework. We show that there is no structural relationship running from the term premium to economic activity, but a reduced-form empirical analysis does suggest that a decline in the term premium has typically been associated with stimulus to real economic activity, which contradicts earlier results in the literature.Interest rates ; Economic forecasting ; Econometric models

    Life prediction and constitutive models for engine hot section anisotropic materials program

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    This report presents the results of the first year of a program designed to develop life prediction and constitutive models for two coated single crystal alloys used in gas turbine airfoils. The two alloys are PWA 1480 and Alloy 185. The two oxidation resistant coatings are PWA 273, an aluminide coating, and PWA 286, an overlay NiCoCrAlY coating. To obtain constitutive and/or fatigue data, tests were conducted on coated and uncoated PWA 1480 specimens tensilely loaded in the 100 , 110 , 111 , and 123 directions. A literature survey of constitutive models was completed for both single crystal alloys and metallic coating materials; candidate models were selected. One constitutive model under consideration for single crystal alloys applies Walker's micromechanical viscoplastic formulation to all slip systems participating in the single crystal deformation. The constitutive models for the overlay coating correlate the viscoplastic data well. For the aluminide coating, a unique test method is under development. LCF and TMF tests are underway. The two coatings caused a significant drop in fatigue life, and each produced a much different failure mechanism

    Electron Bernstein waves in spherical tokamak plasmas with "magnetic wells"

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    In addition to traditional regimes with monotonously increasing magnetic field, regimes with "magnetic wells" also occur in spherical tokamaks (STs). The magnetic field profile inversion modifies significantly the whole picture of the wave propagation and damping. Since the magnetic wells may become quite common with further improvement of ST performance, analysis of such configurations is of interest for assessment of EBW plasma heating an CD perspectives. In this paper the basic features of the EBWs propagation and damping for the second cyclotron harmonic in a slab model are considered.Comment: Proc. of 13-th Joint Workshop on ECE and ECRH, N.Novgorod, Russia May 17-20, 2004, 8 pages, 4 fig

    The owl spreads its wings: global and international education within the local from critical perspectives

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    Within an era of a New Knowledge Society, assumptions abound regarding the ‘goodness' and justice of global interconnections and distributions of knowledge through international educational organizations and structures worldwide. Just as George Bush Jr. in attempting to justify the invasion of Iraq made claim to the democratic goodness of the US ‘spreading their freedoms' in the interests of an all-encompassing democratization of the world, so the assumption that sharing educational knowledge, especially an ‘all-knowing North' with a ‘helpless South' is without question for the greater good of all humanity

    A search for 183-GHz emission from water in late-type stars

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    A search was made for 183 GHz line emission from water vapor in the direction of twelve Mira and two semiregular variables. Upper limits to the emission are in the range of 2000 to 5000 Jy. It is estimated that thermal emission from the inner regions of late type stellar envelopes will be on the order of ten Jy. Maser emission, according to one model, would be an order of magnitude stronger. From the limited set sampled, the possibility of very strong maser emission at 183 GHz cannot yet be ruled out

    A Coulomb Gauge Model of Mesons

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    A model of mesons which is based on the QCD Hamiltonian in Coulomb gauge is presented. The model relies on a novel quasiparticle basis to improve the reliability of the Fock space expansion. It is also relativistic, yields chiral pions, and is tightly constrained by QCD (quark masses are the only parameters). Applications to hidden flavor mesons yield results which are comparable to phenomenological constituent quark models while revealing the limitations of such models.Comment: 13 pages, 1 eps figure, 5 table

    Inflation Assisted by Heterotic Axions

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    We explore the possibility of obtaining inflation in weakly coupled heterotic string theory, where the model dependent axions are responsible for driving inflation. This model can be considered as a certain extrapolation of m2ϕ2m^{2}\phi^{2}-inflation, and is an attempt to explicitly realize the so called N-flation proposal in string theory. The instanton generated potential for the axions essentially has two parameters; a natural mass scale MM and the string coupling gsg_{s}. For isotropic compactifications leading to of order O(104)\mathcal{O} (10^4) axions in the four dimensional spectrum we find that with (M,gs)≃(MGUT,0.5)(M, g_{s})\simeq(M_{GUT}, 0.5) the observed temperature fluctuations in the CMB are correctly reproduced. We assume an initially random distribution for the vevs of the axions. The spectral index, nsn_{s}, is generically more red than for m2ϕ2m^{2}\phi^{2}-inflation. The greater the vevs, the more red the spectral index becomes. Allowing for a wide range of vevs 55 ee-foldings from the end of inflation, we find 0.946≲ns≲0.9620.946\lesssim n_{s} \lesssim 0.962. The tensor-to-scalar ratio, rr, is more sensitive to the vevs, but typically smaller than in m2ϕ2m^{2}\phi^{2}-inflation. Furthermore, in the regime where the leading order theory is valid, rr is bounded by r<0.10r < 0.10. The spectral index and the tensor-to-scalar ratio are correlated. For example, ns≃0.951n_{s}\simeq 0.951 corresponds to r≃0.036r\simeq 0.036.Comment: 1+21 pages, 2 figures, v2: Typos corrected, v3: Typos, very minor corrections, reference added, to appear in JCA

    Canonical Transformations and Path Integral Measures

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    This paper is a generalization of previous work on the use of classical canonical transformations to evaluate Hamiltonian path integrals for quantum mechanical systems. Relevant aspects of the Hamiltonian path integral and its measure are discussed and used to show that the quantum mechanical version of the classical transformation does not leave the measure of the path integral invariant, instead inducing an anomaly. The relation to operator techniques and ordering problems is discussed, and special attention is paid to incorporation of the initial and final states of the transition element into the boundary conditions of the problem. Classical canonical transformations are developed to render an arbitrary power potential cyclic. The resulting Hamiltonian is analyzed as a quantum system to show its relation to known quantum mechanical results. A perturbative argument is used to suppress ordering related terms in the transformed Hamiltonian in the event that the classical canonical transformation leads to a nonquadratic cyclic Hamiltonian. The associated anomalies are analyzed to yield general methods to evaluate the path integral's prefactor for such systems. The methods are applied to several systems, including linear and quadratic potentials, the velocity-dependent potential, and the time-dependent harmonic oscillator.Comment: 28 pages, LaTe
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