Dynamics and stability of wind turbine generators

Synchronous and induction generators are considered. A comparison is made between wind turbines, steam, and hydro units. The unusual phenomena associated with wind turbines are emphasized. The general control requirements are discussed, as well as various schemes for torsional damping such as speed sensitive stabilizer and blade pitch control. Integration between adjacent wind turbines in a wind farm is also considered

Electron collision cross sections in metal vapors Semiannual report

Electron collision cross section in metal vapors - measurement of Townsend alpha coefficient in cesium-helium mixture

Very Massive Stars and the Eddington Limit

We use contemporary evolutionary models for Very Massive Stars (VMS) to assess whether the Eddington limit constrains the upper stellar mass limit. We also consider the interplay between mass and age for the wind properties and spectral morphology of VMS, with reference to the recently modified classification scheme for O2-3.5If*/WN stars. Finally, the death of VMS in the local universe is considered in the context of pair instability supernovae.Comment: 6 pages, 4 figures, from "Four Decades of Massive Star Research" (Quebec, Jul 2011), ASP Conf Ser, in press (L. Drissen, C. Robert, N. St-Louis, A.F.J. Moffat, eds.

Media Coverage of LGBT Issues: Legal, Religious, and Political Frames

This project creates an original dataset of 1,008 randomly sampled news items that discussed LGBT political issues posted online between 2011 and 2017 by Huffington Post Queer Voices, NPR, and Fox News. I use quantitative methods and content analysis to locate the 14 most popular LGBT political issues in media coverage and to confirm there are three competing media frames of political discussion in coverage of LGBT political issues. There are three results chapters. Chapter 5 describes the 14 LGBT political issues that appear most often in political science research and to what extent media coverage of these 14 issues differs across the political left, right and center. I find that academia addresses more LGBT issues, more often, than does media coverage. Also, media coverage and academic literature contain four competing narratives about LGBT people and issues: a Family Narrative, an Identity Narrative, a Tragedy Narrative, and a Political Activity Narrative. Moreover, politically left media coverage is more like academic discussions about LGBT politics than politically right or centrist media coverage. Chapter 6 describes three competing frames in media coverage. A legal frame contains language that discusses constitutions, trial and appellate courts, litigation tactics, and appellate procedure. A religious frame contains language that discusses the Bible, Jesus, religious-based curative therapy, evangelicals as political participants, and quotes from clergy. An institutional frame contains language that involves elections, political parties, direct democracy, constitutional amendments, local state and federal legislatures, and the President. I find that legal framing of LGBT issues has increased since the 2000s, while religious framing has declined, and political framing is slowly rising – peaking in federal election years then decreasing in non-election years. Chapter 7 describes how the media’s focus on same-sex marriage eclipses coverage of less-covered, but still important, LGBT political issues. Further, since same-sex marriage was legalized nation-wide in 2015, the media has been increasingly focused on transgender issues rather than 13 other LGBT political issues. So, the issues, narratives, and frames one encounters in news coverage about the LGBT is noticeably different than in the 2000s, and differs on the political left, right, and center

Reviews

Nasionale Terminologiediens van die Departement van Kuns, Kultuur,Wetenskap en Tegnologie. Dfukkerswoordeboek / Printing Dictionary,Afrikaans-English / English-Afrikaans, hersiene uitgawe, 1995, xviii +309 pp. ISBN 0-621-17323-1. E-pos: [email protected]. Pretoria:Staatsdrukker. Prys R20,20

All Maximally Entangled Four Qubits States

We find an operational interpretation for the 4-tangle as a type of residual entanglement, somewhat similar to the interpretation of the 3-tangle. Using this remarkable interpretation, we are able to find the class of maximally entangled four-qubits states which is characterized by four real parameters. The states in the class are maximally entangled in the sense that their average bipartite entanglement with respect to all possible bi-partite cuts is maximal. We show that while all the states in the class maximize the average tangle, there are only few states in the class that maximize the average Tsillas or Renyi $\alpha$-entropy of entanglement. Quite remarkably, we find that up to local unitaries, there exists two unique states, one maximizing the average $\alpha$-Tsallis entropy of entanglement for all $\alpha\geq 2$, while the other maximizing it for all $0<\alpha\leq 2$ (including the von-Neumann case of $\alpha=1$). Furthermore, among the maximally entangled four qubits states, there are only 3 maximally entangled states that have the property that for 2, out of the 3 bipartite cuts consisting of 2-qubits verses 2-qubits, the entanglement is 2 ebits and for the remaining bipartite cut the entanglement between the two groups of two qubits is 1ebit. The unique 3 maximally entangled states are the 3 cluster states that are related by a swap operator. We also show that the cluster states are the only states (up to local unitaries) that maximize the average $\alpha$-Renyi entropy of entanglement for all $\alpha\geq 2$.Comment: 15 pages, 2 figures, Revised Version: many references added, an appendix added with a statement of the Kempf-Ness theore

The effect of a massive object on an expanding universe

A tetrad-based procedure is presented for solving Einstein's field equations for spherically-symmetric systems; this approach was first discussed by Lasenby et al. in the language of geometric algebra. The method is used to derive metrics describing a point mass in a spatially-flat, open and closed expanding universe respectively. In the spatially-flat case, a simple coordinate transformation relates the metric to the corresponding one derived by McVittie. Nonetheless, our use of non-comoving (`physical') coordinates greatly facilitates physical interpretation. For the open and closed universes, our metrics describe different spacetimes to the corresponding McVittie metrics and we believe the latter to be incorrect. In the closed case, our metric possesses an image mass at the antipodal point of the universe. We calculate the geodesic equations for the spatially-flat metric and interpret them. For radial motion in the Newtonian limit, the force acting on a test particle consists of the usual $1/r^2$ inwards component due to the central mass and a cosmological component proportional to $r$ that is directed outwards (inwards) when the expansion of the universe is accelerating (decelerating). For the standard $\Lambda$CDM concordance cosmology, the cosmological force reverses direction at about $z\approx 0.67$. We also derive an invariant fully general-relativistic expression, valid for arbitrary spherically-symmetric systems, for the force required to hold a test particle at rest relative to the central point mass.Comment: 14 pages, 2 tables, 5 figures; new version, to match the version published in MNRA

The incidence of sudden unexpected death in epilepsy (sudep) in south dublin and wicklow

Patients with epilepsy have a mortality rate higher than that of the general population. Some of this excess mortality is attributable to sudden unexpected death (SUDEP). We examined the incidence of this phenomenon both retrospectively and prospectively in the population of South Dublin and Wicklow over the period May 1992–1995. Cases were ascertained by examination of post-mortem registers of hospitals serving the area studied. Information on cases was sought from hospital records, general practitioners and families. Fifteen cases (10 male, five female) were identified resulting in an overall incidence rate of SUDEP of 1:680/year for the 3 years of the study. This is the only study of incidence of SUDEP conducted in Ireland and our results are in keeping with incidence rates elsewhere in Europe and the USA

Guest Editorial - Special Issue June 2016: ESLTIS 2015 - Conference Special Issue

In this short editorial, we’ll discuss the evolution of the inaugural Enhancing Student Learning through Innovative Scholarship conference, of which this volume contains contributed papers. This conference, the first national meeting open to all teaching (as opposed to research) focussed academic took place in Durham in July 2015