Evaluation of the effects of rotor harmonics in a doubly-fed induction generator with harmonic induced speed ripple

This paper is concerned with the low-frequency harmonics which originate from the rotor inverter of a doubly-fed induction generator (DFIG). By including the mechanical speed response, it expands the transformer approach previously taken to analyze the harmonic transfer in the machine. A numerical method is proposed to calculate the stator current sidebands, which can be used to predict the voltage fluctuation at the system busbar. It is shown that the pulsating torque associated with the rotor harmonics can induce speed ripple depending on the inertia, causing a significant change in the stator current spectrum. Experiment and simulation verify the analysis and the proposed calculation method

Flux profile scanners for scattered high-energy electrons

The paper describes the design and performance of flux integrating Cherenkov scanners with air-core reflecting light guides used in a high-energy, high-flux electron scattering experiment at the Stanford Linear Accelerator Center. The scanners were highly radiation resistant and provided a good signal to background ratio leading to very good spatial resolution of the scattered electron flux profile scans.Comment: 22 pages, 17 figure

Positivity constraints for lepton polarization in neutrino deep inelastic scattering

We consider the spin polarization of leptons produced in neutrino and antineutrino nucleon deep inelastic scattering, via charged currents, and we study the positivity constraints on the spin components in a model independent way. These results are very important, in particular in the case of $\tau^{\pm}$ leptons, because the polarization information is crucial in all future neutrino oscillation experiments.Comment: 14 pages, 4 figure

A survey of the ichthyofauna in the Noetsie Estuary, Western Cape Province, South Africa

The fish assemblage in the Noetsie Estuary, a temporarily open and closed estuary on the southern coast of South Africa, was sampled using multiple gears. A total of 12 species from 8 families were recorded. Collectively, estuarine-dependent marine species dominated seine net catches numerically and in terms of biomass for both sampling seasons. Estuarine round herring (Gilchristella aestuaria) was numerically the dominant species in late summer, while juvenile Mugilidae dominated catches in winter. Size class distributions of various fish species indicate that the estuary both serves a nursery function for important euryhaline marine species and supports estuarine resident taxa. Application of the Estuarine Fish Community Index indicates the ecological condition of the estuary to be ‘good’. This study contributes to the species list for the estuary while also reporting the presence of an alien invasive freshwater species, Gambusia affinis. Recommendations include the development of a management plan and the formalisation of an estuarine management committee. Conservation implications: The Noetsie Estuary serves a nursery function for important euryhaline marine species, while supporting healthy populations of estuarine resident taxa. The presence of one alien invasive fish species is documented with potential implications for the conservation of biodiversity in the estuary

What is the evidence-base for atopic eczema treatments? A summary of published randomised controlled trials

Atopic eczema (AE) is a common chronic inflammatory skin condition. Whilst many AE treatment options are available, the evidence to support their efficacy varies in depth and quality. In 2000, an NIHR HTA systematic review identified and evaluated existing randomised controlled trials (RCTs) of AE treatments. To ensure continuing utility, the NIHR commissioned an update to the review. Here, we present an overview of the updated report and key findings. Systematic reviews and RCTs of AE treatments that included participants with AE (criteria based or diagnosed) were identified using: MEDLINE, EMBASE, CENTRAL, LILACS, AMED, CINAHL and Cochrane Skin Group Specialised Register (searched to August 31st 2013 (RCTs) and 31st December 2015 (systematic reviews)). Outcome measures included: symptoms, AE severity, quality-of-life, and adverse effects. Study quality was assessed using the Cochrane Collaboration risk of bias tool. Of the 287 new RCTs identified, only 22 (8%) were judged to be low risk of bias. When combined with RCTs from the previous review (n= 254), we found ‘reasonable evidence of benefit’ for corticosteroids, calcineurin inhibitors, Atopiclair™, ciclosporin, azathioprine, ultraviolet light and education programmes. Interventions with reasonable evidence of ‘no benefit’ included some dietary interventions, ion exchange water softeners, multiple daily applications of topical corticosteroids and antibiotic-containing corticosteroids for non-infected AE. Many common treatments lack evidence of efficacy and warrant further evaluation. The evidence base for AE is still hampered by poor trial design and reporting. The trials included in this review were used to establish the Global Resource of Eczema Trials (GREAT) Database

Gravitational waves from coalescing binaries: detection strategies and Monte Carlo estimation of parameters

The paper deals with issues pertaining the detection of gravitational waves from coalescing binaries. We introduce the application of differential geometry to the problem of optimal detection of the `chirp signal'. We have also carried out extensive Monte Carlo simulations to understand the errors in the estimation of parameters of the binary system. We find that the errors are much more than those predicted by the covariance matrix even at a high SNR of 10-15. We also introduce the idea of using the instant of coalescence rather than the time of arrival to determine the direction to the source.Comment: 28 pages, REVTEX, 12 figures (bundled via uufiles command along with this paper) submitted to Phys. Rev.

D-Brane Dynamics and NS5 Rings

We consider the classical motion of a probe D-brane moving in the background geometry of a ring of NS5 branes, assuming that the latter are non-dynamical. We analyse the solutions to the Dirac-Born-Infield (DBI) action governing the approximate dynamics of the system. In the near horizon (throat) approximation we find several exact solutions for the probe brane motion. These are compared to numerical solutions obtained in more general cases. One solution of particular interest is when the probe undergoes oscillatory motion through the centre of the ring (and perpendicular to it). By taking the ring radius sufficiently large, this solution should remain stable to any stringy corrections coming from open-strings stretching between the probe and the NS5-branes along the ring.Comment: 17 pages, Latex, 8 figures; References adde

That's a wrap!

Calibration technology provides us with a fast and elegant way to find the supergravity solutions for BPS wrapped M-branes. Its true potential had however remained untapped due to the absence of a classification of calibrations in spacetimes with non-trivial flux. The applications of this method were thus limited in practise to M-branes wrapping Kahler calibrated cycles. In this paper, we catagorize a type of generalised calibrations which exist in supergravity backgrounds and contain Kahler calibrations as a sub-class. This broadens the arena of brane configurations whose supergravity solutions are accessible through the calibration 'short-cut' method.Comment: 19 pages, typos correcte

Finite-temperature Fermi-edge singularity in tunneling studied using random telegraph signals

We show that random telegraph signals in metal-oxide-silicon transistors at millikelvin temperatures provide a powerful means of investigating tunneling between a two-dimensional electron gas and a single defect state. The tunneling rate shows a peak when the defect level lines up with the Fermi energy, in excellent agreement with theory of the Fermi-edge singularity at finite temperature. This theory also indicates that defect levels are the origin of the dissipative two-state systems observed previously in similar devices.Comment: 5 pages, REVTEX, 3 postscript figures included with epsfi

M2-branes wrapped on holomorphic curves

The generalised calibration for a wrapped membrane is gauge equivalent to the supergravity three-form under which the membrane is electrically charged. Given the relevant calibration, one can go a long way towards constructing the supergravity solution for the wrapped brane. Applications of this method have been restricted since generalised calibrations have not yet been completely classified in spacetimes with non-vanishing flux. In this paper, we take a first step towards such a classification by studying membranes wrapping holomorphic curves. Supersymmetry preservation imposes a constraint on the Hermitean metric in the embedding space and it is found that this can be expressed as a restriction on possible generalised calibrations. Allowed calibrations in a particular spacetime are simply those which satisfy the constraint equation relevant to that background; in particular, we see that the previously considered Kahler calibrations are just a subclass of possible solutions.Comment: Discussion clarified, typos corrected, references updated. Results remain unchanged. 12 page