15,079 research outputs found

    Quantitative Measurements in the Transmission in Solid Acoustic Wave Filters with Varying Physical Dimensions

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    The object of these experiments was to test the transmission of solid acoustic wave filters with the view to the establishment of empirical formulas to be used in future designs. The length of sections, the conductivity into the branch lines, and the volume of the branch lines were altered in the case of low-frequency-pass-filters. In all cases the variations produced effects that are analogous to those found with acoustic wave filters in fluids. But more than this, so far as a test has been made, the cut-off frequency is in agreement with the Stewart theory for fluids. This means that the phenomena is caused almost exclusively by the longitudinal waves. Moreover, recurring bands were found in high frequencies and these seemed to be in accord with the more extended theory of Stewart concerning the presence of such additional bands. The conclusion in that the acoustic wave filters in solids can be designated on the basis of the formulas obtained for fluids

    Investigation of kilovolt ion sputtering Quarterly progress report, May - Jul. 1966

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    Aluminum sputtering, and neutron activation analysis after cesium ion bombardmen

    The burrowing beetles of the genus Mycotrupes (Coleoptera: Scarabaeidae: Geotrupinae)

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    http://deepblue.lib.umich.edu/bitstream/2027.42/56329/1/MP084.pd

    Nonequilibrium Approach to Bloch-Peierls-Berry Dynamics

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    We examine the Bloch-Peierls-Berry dynamics under a classical nonequilibrium dynamical formulation. In this formulation all coordinates in phase space formed by the position and crystal momentum space are treated on equal footing. Explicitly demonstrations of the no (naive) Liouville theorem and of the validity of Darboux theorem are given. The explicit equilibrium distribution function is obtained. The similarities and differences to previous approaches are discussed. Our results confirm the richness of the Bloch-Peierls-Berry dynamics

    Direct observation of particle-hole mixing in the superconducting state by angle-resolved photoemission

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    Particle-hole (p-h) mixing is a fundamental consequence of the existence of a pair condensate. We present direct experimental evidence for p-h mixing in the angle-resolved photoemission (ARPES) spectra in the superconducting state of Bi_2Sr_2CaCu_2O_{8+\delta}. In addition to its pedagogical importance, this establishes unambiguously that the gap observed in ARPES is associated with superconductivity.Comment: 3 pages, revtex, 4 postscript figure

    Superconducting Fluxon Pumps and Lenses

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    We study stochastic transport of fluxons in superconductors by alternating current (AC) rectification. Our simulated system provides a fluxon pump, "lens", or fluxon "rectifier" because the applied electrical AC is transformed into a net DC motion of fluxons. Thermal fluctuations and the asymmetry of the ratchet channel walls induce this "diode" effect, which can have important applications in devices, like SQUID magnetometers, and for fluxon optics, including convex and concave fluxon lenses. Certain features are unique to this novel two-dimensional (2D) geometric pump, and different from the previously studied 1D ratchets.Comment: Phys. Rev. Lett. 83, in press (1999); 4 pages, 5 .gif figures; figures also available at http://www-personal.engin.umich.edu/~nori/ratche

    A System for Accessible Artificial Intelligence

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    While artificial intelligence (AI) has become widespread, many commercial AI systems are not yet accessible to individual researchers nor the general public due to the deep knowledge of the systems required to use them. We believe that AI has matured to the point where it should be an accessible technology for everyone. We present an ongoing project whose ultimate goal is to deliver an open source, user-friendly AI system that is specialized for machine learning analysis of complex data in the biomedical and health care domains. We discuss how genetic programming can aid in this endeavor, and highlight specific examples where genetic programming has automated machine learning analyses in previous projects.Comment: 14 pages, 5 figures, submitted to Genetic Programming Theory and Practice 2017 worksho

    Formation of cosmological mass condensation within a FRW universe: exact general relativistic solutions

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    Within the framework of an exact general relativistic formulation of gluing manifolds, we consider the problem of matching an inhomogeneous overdense region to a Friedmann-Robertson-Walker background universe in the general spherical symmetric case of pressure-free models. It is shown that, in general, the matching is only possible through a thin shell, a fact ignored in the literature. In addition to this, in subhorizon cases where the matching is possible, an intermediate underdense region will necessarily arise.Comment: 6 page

    Hall of Mirrors Scattering from an Impurity in a Quantum Wire

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    This paper develops a scattering theory to examine how point impurities affect transport through quantum wires. While some of our new results apply specifically to hard-walled wires, others--for example, an effective optical theorem for two-dimensional waveguides--are more general. We apply the method of images to the hard-walled guide, explicitly showing how scattering from an impurity affects the wire's conductance. We express the effective cross section of a confined scatterer entirely in terms of the empty waveguide's Green's function, suggesting a way in which to use semiclassical methods to understand transport properties of smooth wires. In addition to predicting some new phenomena, our approach provides a simple physical picture for previously observed effects such as conductance dips and confinement-induced resonances.Comment: 19 pages, 8 figures. Accepted for publication in Physical Review B. Minor additions to text, added reference
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