801 research outputs found

    Design and Validation of a Synchronous Reluctance Motor With Single Tooth Windings

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    This paper presents for the first time the analysis and experimental validation of a six-slot four-pole synchronous reluctance motor with nonoverlapping fractional slot-concentrated windings. The machine exhibits high torque density and efficiency due to its high fill factor coils with very short end windings, facilitated by a segmented stator and bobbin winding of the coils. These advantages are coupled with its inherent robustness and low cost. The topology is presented as a logical step forward in advancing synchronous reluctance machines that have been universally wound with a sinusoidally distributed winding. The paper presents the motor design, performance evaluation through finite element studies and validation of the electromagnetic model, and thermal specification through empirical testing. It is shown that high performance synchronous reluctance motors can be constructed with single tooth wound coils, but considerations must be given regarding torque quality and the d-q axis inductances

    Chapter 14: Vulnerability of seabirds on the Great Barrier Reef to climate change

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    Seabirds are highly visible, charismatic predators in marine ecosystems that are defined as feeding exclusively at sea, in either nearshore, offshore or pelagic waters. At a conservative estimate there are approximately 0.7 billion individuals of 309 species of seabirds globally. Such high population abundance means that in all ecosystems where seabirds occur the levels of marine resources they consume are significant. Such high consumption rates also mean that seabirds play a number of important functional roles in marine ecosystems, including the transfer of nutrients from offshore and pelagic areas to islands and reefs, seed dispersal and the distribution of organic matter into lower parts of the developing soil profile (eg burrow-nesting species such as shearwaters).This is Chapter 14 of Climate change and the Great Barrier Reef: a vulnerability assessment. The entire book can be found at http://hdl.handle.net/11017/13

    A gauge model for quantum mechanics on a stratified space

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    In the Hamiltonian approach on a single spatial plaquette, we construct a quantum (lattice) gauge theory which incorporates the classical singularities. The reduced phase space is a stratified K\"ahler space, and we make explicit the requisite singular holomorphic quantization procedure on this space. On the quantum level, this procedure furnishes a costratified Hilbert space, that is, a Hilbert space together with a system which consists of the subspaces associated with the strata of the reduced phase space and of the corresponding orthoprojectors. The costratified Hilbert space structure reflects the stratification of the reduced phase space. For the special case where the structure group is SU(2)\mathrm{SU}(2), we discuss the tunneling probabilities between the strata, determine the energy eigenstates and study the corresponding expectation values of the orthoprojectors onto the subspaces associated with the strata in the strong and weak coupling approximations.Comment: 38 pages, 9 figures. Changes: comments on the heat kernel and coherent states have been adde

    An in vitro model for assessing effective scrapie decontamination

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    Scrapie infectivity enters the environment via a multiplicity of routes from infected animals. Environmentally associated scrapie persists on farms when infected animals have been removed and is particularly resistant to disinfection. Infectivity within the farm is not adequately removed by current recommended guidelines for farm decontamination. We describe an in vitro method for modelling decontamination, specifically the removal of scrapie prions from the surface of concrete fomites within buildings that have housed scrapie infected animals. Concrete that had been spiked with low amounts of a diluted scrapie positive brain homogenate was sampled before and after decontamination. Extracts were used to seed a semi-quantitative serial protein misfolding cyclic amplification assay (sPMCA). We demonstrate that methods currently recommended for prion decontamination result in inadequate reduction of prion seeding activity within this in vitro assay. Effective treatment was achieved using repeat dosing of surfaces with 20,000 ppm available chlorine for 4 h

    The Net Global Effects of Alternative U.S. Biofuel Mandates

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    One of the declared objectives of U.S. biofuel policy is the reduction of greenhouse gas (GHG) emissions from fossil fuel combustion, but many studies have questioned whether such a reduction would actually occur and, if so, how large it would be. This report describes the global market, land use, GHG emissions, and nitrogen use impacts of the U.S. Renewable Fuel Standard (RFS2) and several alternative biofuel policy designs, which differ in terms of mandate magnitude and feedstock composition, over the 2010-2030 period

    Flavour and Collider Interplay for SUSY at LHC7

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    The current 7 TeV run of the LHC experiment shall be able to probe gluino and squark masses up to values larger than 1 TeV. Assuming that hints for SUSY are found in the jets plus missing energy channel by the end of a 5 fb1^{-1} run, we explore the flavour constraints on three models with a CMSSM-like spectrum: the CMSSM itself, a Seesaw extension of the CMSSM, and Flavoured CMSSM. In particular, we focus on decays that might have been measured by the time the run is concluded, such as BsμμB_s\to\mu\mu and μeγ\mu\to e\gamma. We also analyse constraints imposed by neutral meson bounds and electric dipole moments. The interplay between collider and flavour experiments is explored through the use of three benchmark scenarios, finding the flavour feedback useful in order to determine the model parameters and to test the consistency of the different models.Comment: 44 pages, 15 figures; v3: minor corrections, added references, updated figures. Version accepted for publicatio

    4pi Models of CMEs and ICMEs

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    Coronal mass ejections (CMEs), which dynamically connect the solar surface to the far reaches of interplanetary space, represent a major anifestation of solar activity. They are not only of principal interest but also play a pivotal role in the context of space weather predictions. The steady improvement of both numerical methods and computational resources during recent years has allowed for the creation of increasingly realistic models of interplanetary CMEs (ICMEs), which can now be compared to high-quality observational data from various space-bound missions. This review discusses existing models of CMEs, characterizing them by scientific aim and scope, CME initiation method, and physical effects included, thereby stressing the importance of fully 3-D ('4pi') spatial coverage.Comment: 14 pages plus references. Comments welcome. Accepted for publication in Solar Physics (SUN-360 topical issue

    Observation of the Ankle and Evidence for a High-Energy Break in the Cosmic Ray Spectrum

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    We have measured the cosmic ray spectrum at energies above 101710^{17} eV using the two air fluorescence detectors of the High Resolution Fly's Eye experiment operating in monocular mode. We describe the detector, PMT and atmospheric calibrations, and the analysis techniques for the two detectors. We fit the spectrum to models describing galactic and extragalactic sources. Our measured spectrum gives an observation of a feature known as the ``ankle'' near 3×10183\times 10^{18} eV, and strong evidence for a suppression near 6×10196\times 10^{19} eV.Comment: 14 pages, 9 figures. To appear in Physics Letters B. Accepted versio

    Svestka's Research: Then and Now

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    Zdenek Svestka's research work influenced many fields of solar physics, especially in the area of flare research. In this article I take five of the areas that particularly interested him and assess them in a "then and now" style. His insights in each case were quite sound, although of course in the modern era we have learned things that he could not readily have envisioned. His own views about his research life have been published recently in this journal, to which he contributed so much, and his memoir contains much additional scientific and personal information (Svestka, 2010).Comment: Invited review for "Solar and Stellar Flares," a conference in honour of Prof. Zden\v{e}k \v{S}vestka, Prague, June 23-27, 2014. This is a contribution to a Topical Issue in Solar Physics, based on the presentations at this meeting (Editors Lyndsay Fletcher and Petr Heinzel
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