1,940 research outputs found

    Maximal Complexifications of Certain Riemannian Homogeneous Manifolds

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    A characterization of maximal domains of existence of adapted complex structures for Riemannian homogeneous manifolds under certain extensibility assumptions on their geodesic flow is given. This is applied to generalized Heisenberg groups and naturally reductive Riemannian homogeneous spaces. As an application it is shown that the case of generalized Heisenberg groups yields examples of maximal domains of definition for the adapted complex structure which are are neither holomorphically separable, nor holomorphically convex.Comment: 18 pages, LaTeX-fil

    Info Lit 2.0 or Deja Vu?

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    In 1999, ACRL convened a national task force to draft Information Literacy Competency Standards for Higher Education. ACRL has recently launched a revision to those standards. The original standards were influential because they helped advance a national need in higher education at the time: a shift to outcomes based learning. Thirteen years later, information literacy stands alongside oral and written communication, critical thinking and ethical reasoning as learning outcomes broadly acknowledged as needing to be integrated, with disciplinary content, into the curriculum. This author believes that, in contrast to the first process, the current recommendations for revision are focused on the wrong question and include the wrong people to address it. Out of the eight recommendations in the task force report, seven focus on revising articulation of the learning outcomes and the eighth calls for better alignment with theAmerican Association of School Librarians’ Standards for the 21st Century Learner. It is time to let go of the rehashing and professional naval gazing and look ahead to address the issues that are most pressing in higher education now. The point isn\u27t to further define, redefine and write more, less or different learning outcomes. There is little to gain in continuing the decades old “literacies “debate about whose are most important and which should be integrated into the curriculum. Labels do not matter! No organization or individual institution is going to accept detailed learning outcomes anyway. Information literacy as a phrase and as a set of learning outcomes are already integrated into a host of related skills, regardless of the label. The challenge now is to move ahead and address the current concerns of education reform: vertical integration with disciplinary knowledge, curriculum mapping, and assessment. There are a host of challenges and libraries and librarians are perfectly poised to help. I have moved on, so should ACRL

    Progress towards Bell-type polarization experiment with thermal neutrons

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    Experimental tests of Bell-type inequalities distinguishing between quantum mechanics and local realistic theories remain of considerable interest if performed on massive particles, for which no conclusive result has yet been obtained. Only two-particle experiments may specifically test the concept of spatial nonlocality in quantum theory, whereas single-particle experiments may generally test the concept of quantum noncontextuality. Here we have performed the first Bell-type experiment with a beam of thermal-neutron pairs in the singlet state of spin, as originally suggested by J. S. Bell. These measurements confirm the quantum-theoretical predictions, in agreement with the results of the well-known polarization experiments carried out on optical photons years ago

    The Effects of Boxy/Peanut Bulges on Galaxy Models

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    We examine the effects that the modelling of a Boxy/Peanut (B/P) bulge will have on the estimates of the stellar gravitational potential, forces, orbital structure and bar strength of barred galaxies. We present a method for obtaining the potential of disc galaxies from surface density images, assuming a vertical density distribution (height function), which is let to vary with position, thus enabling it to represent the geometry of a B/P. We construct a B/P height function after the results from a high-resolution, N-body+SPH simulation of an isolated galaxy and compare the resulting dynamical model to those obtained with the commonly used, position-independent "flat" height functions. We show that methods that do not allow for a B/P can induce errors in the forces in the bar region of up to 40% and demonstrate that this has a significant impact on the orbital structure of the model, which in turn determines its kinematics and morphology. Furthermore, we show that the bar strength is reduced in the presence of a B/P. We conclude that neglecting the vertical extent of a B/P can introduce considerable errors in the dynamical modelling. We also examine the errors introduced in the model due to uncertainties in the parameters of the B/P and show that even for generous but realistic values of the uncertainties, the error will be noticeably less than that of not modelling a B/P bulge at all.Comment: Accepted for publication in MNRA

    Battery losses in a MMC for BEVS application

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    Objective: This paper analyses the Modular Multilevel Converter (MMC) topology, where each individual Sub Module (SM), in half bridge configuration, is directly fed by an elementary electrochemical cell. Methods: The aim is to investigate how the reference voltages influence the cells currents waveforms, determining how the active powers and the losses are distributed among the cells. Considering a 2-level Voltage Source Inverter (VSI) topology working in the same conditions, the ratio between the MMC total cells losses and VSI total cells losses is calculated. After showing the system architecture and mathematical model, the cells current waveform investigation is presented and detailed both for triangular and sinusoidal voltage reference waveform

    Further evidence of antibunching of two coherent beams of fermions

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    We describe an experiment confirming the evidence of the antibunching effect on a beam of non interacting thermal neutrons. The comparison between the results recorded with a high energy-resolution source of neutrons and those recorded with a broad energy-resolution source enables us to clarify the role played by the beam coherence in the occurrence of the antibunching effect.Comment: 4 pages, 3 figure
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