27,221 research outputs found

    A High Phase Advance Damped and Detuned Structure for the Main Linacs of Clic

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    The main accelerating structures for the CLIC are designed to operate at an average accelerating gradient of 100 MV/m. The accelerating frequency has been optimised to 11.994 GHz with a phase advance of 2{\pi}/3 of the main accelerating mode. The moderately damped and detuned structure (DDS) design is being studied as an alternative to the strongly damped WDS design. Both these designs are based on the nominal accelerating phase advance. Here we explore high phase advance (HPA) structures in which the group velocity of the rf fields is reduced compared to that of standard (2{\pi}/3) structures. The electrical breakdown strongly depends on the fundamental mode group velocity. Hence it is expected that electrical breakdown is less likely to occur in the HPA structures. We report on a study of both the fundamental and dipole modes in a CLIC_DDS_HPA structure, designed to operate at 5{\pi}/6 phase advance per cell. Higher order dipole modes in both the standard and HPA structures are also studied

    Enhanced coupling design of a detuned damped structure for clic

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    The key feature of the improved coupling design in the Damped Detuned Structure (DDS) is focused on the four manifolds. Rectangular geometry slots and rectangular manifolds are used. This results in a significantly stronger coupling to the manifolds compared to the previous design. We describe the new design together with its wakefield damping properties.Comment: 3 pages, 8 figures, submitted to IPAC1

    Width of the Zero-Field Superconducting Resistive Transition in the Vicinity of the Localization Threshold

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    Resistive superconducting zero-field transition in amorphous In-O films in states from the vicinity of the insulator-superconductor transition is analyzed in terms of two characteristic temperatures: the upper one, Tc0T_{c0}, where the finite amplitude of the order parameter is established and the lower one, TcT_c, where the phase ordering takes place. It follows from the magnetoresistance measurements that the resistance in between, Tc<T<Tc0T_c<T<T_{c0}, cannot be ascribed to dissipation by thermally dissociated vortex pairs. So, it is not Kosterlitz-Thouless-Berezinskii transition that happens at TcT_c.Comment: 4 pages, 3 figure

    Test particle motion in a gravitational plane wave collision background

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    Test particle geodesic motion is analysed in detail for the background spacetimes of the degenerate Ferrari-Ibanez colliding gravitational wave solutions. Killing vectors have been used to reduce the equations of motion to a first order system of differential equations which have been integrated numerically. The associated constants of the motion have also been used to match the geodesics as they cross over the boundary between the single plane wave and interaction zones.Comment: 11 pages, 6 Postscript figure

    Propofol-alfentanil vs propofol-remifentanil for posterior spinal fusion including wake-up test

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    Background. Wake-up test can be used during posterior spinal fusion (PSF) to ensure that spinal function remains intact. This study aims at assessing the characteristics of the wake-up test during propofol-alfentanil (PA) vs propofol-remifentanil (PR) infusions for PSF surgery. Methods. Sixty patients with scoliosis and candidates for PSF surgery were randomly allocated in either alfentanil (PA) or remifentanil (PR) group. After an i.v. bolus of alfentanil 30 ĂŽÂŒg kg-1 in the PA group or remifentanil 1 ĂŽÂŒg kg-1 in the PR group, anaesthesia was induced with thiopental and atracurium. During maintenance, opioid infusion consisted of alfentanil 1 ĂŽÂŒg kg-1 min-1 or remifentanil 0.2 ĂŽÂŒg kg-1 min-1, in the PA group and the PR group, respectively. All patients received propofol 50 ĂŽÂŒg kg-1 min-1. Atracurium was given to maintain the required surgical relaxation. At the surgeon's request, all infusions were discontinued. Patients were asked to move their hands and feet. Time from anaesthetic discontinuation to spontaneous ventilation (T1), and from then until movement of the hands and feet (T2), and its quality were recorded. Results. The average T1 and T2 were significantly shorter in the PR group 3.6 (2.5) and 4.1 (2) min than the PA group 6.1 (4) and 7.5 (4.5) min. Quality of wake-up test, however, did not show significant difference between the two groups studied. Conclusion. Wake-up test can be conducted faster with remifentanil compared with alfentanil infusion during PSF surgery. © 2006 Oxford University Press

    A review of human error in marine engine maintenance

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    Maritime safety involves minimizing error in all aspects of the marine system. Human error hasreceived much importance, being responsible for about 80% of the maritime accident worldwide. Currently,more attention has been focused to reduce human error in marine engine maintenance. On-board marineengine maintenance activities are often complex, where seafarers conduct maintenance activities in variousmarine environmental (i.e. extreme weather, ship motions, noise, and vibration) and operational (i.e. workoverload and stress) conditions. These environmental and operational conditions, in combination with generichuman error tendencies, results in innumerable forms of error. There are numerous accidents that happeneddue to the human error during the maintenance activities of a marine engine. The most severe human errorresults in accidents due to is a loss of life. Moreover, there are other consequences too such as delaying theproductivity of marine operations which results in the financial loss. This study reviews methods that arecurrently available for identifying, reporting and managing human error in marine engine maintenance. As abasis for this discussion, authors provide an overview of approaches for investigating human error, and adescription of marine engine maintenance activities and environmental and operational characteristics

    Role of bulk and surface phonons in the decay of metal surface states

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    We present a comprehensive theoretical investigation of the electron-phonon contribution to the lifetime broadening of the surface states on Cu(111) and Ag(111), in comparison with high-resolution photoemission results. The calculations, including electron and phonon states of the bulk and the surface, resolve the relative importance of the Rayleigh mode, being dominant for the lifetime at small hole binding energies. Including the electron-electron interaction, the theoretical results are in excellent agreement with the measured binding energy and temperature dependent lifetime broadening.Comment: 4 pages, 3 figure

    Radiative corrections to deep-inelastic ed−ed- scattering. Case of tensor polarized deuteron

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    The model-independent radiative corrections to deep-inelastic scattering of unpolarized electron beam off the tensor polarized deuteron target have been considered. The contribution to the radiative corrections due to the hard-photon emission from the elastic electron-deuteron scattering (the so-called elastic radiative tail) is also investigated. The calculation is based on the covariant parametrization of the deuteron quadrupole polarization tensor. The numerical estimates of the radiative corrections to the polarization observables have been done for the kinematical conditions of the current experiment at HERAComment: 21 pages, 5 figure
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