76 research outputs found
Water drop to metal and water drop to water drop corona discharges
ABSTRACT Water drop corona has been identified by many authors as a major cause of deterioration of silicone rubber high voltage insulation but at this stage there have been no thorough studies made of this phenomenon. In this paper fundamental observations are presented of electrical discharges from water drops, movement of drops, and drop coalescence in the presence of 50 Hz alternating electric fields. Measurements are made both with water drops on metal electrodes and with water drops on the surface of silicone rubber insulation. Comparisons are made of current pulses and atomic emission spectra from previous work by the authors on dry point-plane discharges to provide information about the main types of active species which may cause insulator surface degradation. Visual images of wet electrodes show how water drops can play a part in encouraging flashover. The first reproducible visual images of water drop corona at the triple junction of water air and rubber insulation are presented. The current measurements were captured with a digital oscilloscope sampling at 200 MHz. The time constant of the measuring circuitry was approximately 14 nanoseconds
A general theory of equilibrium selection in games. Chapter 5: The solution concept
Harsanyi JC, Selten R. A general theory of equilibrium selection in games. Chapter 5: The solution concept. Working Papers. Institute of Mathematical Economics. Vol 132. Bielefeld: Center for Mathematical Economics; 1984
Observational and Dynamical Characterization of Main-Belt Comet P/2010 R2 (La Sagra)
We present observations of comet-like main-belt object P/2010 R2 (La Sagra)
obtained by Pan-STARRS 1 and the Faulkes Telescope-North on Haleakala in
Hawaii, the University of Hawaii 2.2 m, Gemini-North, and Keck I telescopes on
Mauna Kea, the Danish 1.54 m telescope at La Silla, and the Isaac Newton
Telescope on La Palma. An antisolar dust tail is observed from August 2010
through February 2011, while a dust trail aligned with the object's orbit plane
is also observed from December 2010 through August 2011. Assuming typical phase
darkening behavior, P/La Sagra is seen to increase in brightness by >1 mag
between August 2010 and December 2010, suggesting that dust production is
ongoing over this period. These results strongly suggest that the observed
activity is cometary in nature (i.e., driven by the sublimation of volatile
material), and that P/La Sagra is therefore the most recent main-belt comet to
be discovered. We find an approximate absolute magnitude for the nucleus of
H_R=17.9+/-0.2 mag, corresponding to a nucleus radius of ~0.7 km, assuming an
albedo of p=0.05. Using optical spectroscopy, we find no evidence of
sublimation products (i.e., gas emission), finding an upper limit CN production
rate of Q_CN<6x10^23 mol/s, from which we infer an H2O production rate of
Q_H2O<10^26 mol/s. Numerical simulations indicate that P/La Sagra is
dynamically stable for >100 Myr, suggesting that it is likely native to its
current location and that its composition is likely representative of other
objects in the same region of the main belt, though the relatively close
proximity of the 13:6 mean-motion resonance with Jupiter and the (3,-2,-1)
three-body mean-motion resonance with Jupiter and Saturn mean that dynamical
instability on larger timescales cannot be ruled out.Comment: 23 pages, 13 figures, accepted for publication in A
Utility of linking primary care electronic medical records with Canadian census data to study the determinants of chronic disease: an example based on socioeconomic status and obesity
Physician privacy concerns when disclosing patient data for public health purposes during a pandemic influenza outbreak
Background: Privacy concerns by providers have been a barrier to disclosing patient information for public health\ud
purposes. This is the case even for mandated notifiable disease reporting. In the context of a pandemic it has been\ud
argued that the public good should supersede an individualâs right to privacy. The precise nature of these provider\ud
privacy concerns, and whether they are diluted in the context of a pandemic are not known. Our objective was to\ud
understand the privacy barriers which could potentially influence family physiciansâ reporting of patient-level\ud
surveillance data to public health agencies during the Fall 2009 pandemic H1N1 influenza outbreak.\ud
Methods: Thirty seven family doctors participated in a series of five focus groups between October 29-31 2009.\ud
They also completed a survey about the data they were willing to disclose to public health units. Descriptive\ud
statistics were used to summarize the amount of patient detail the participants were willing to disclose, factors that\ud
would facilitate data disclosure, and the consensus on those factors. The analysis of the qualitative data was based\ud
on grounded theory.\ud
Results: The family doctors were reluctant to disclose patient data to public health units. This was due to concerns\ud
about the extent to which public health agencies are dependable to protect health information (trusting beliefs),\ud
and the possibility of loss due to disclosing health information (risk beliefs). We identified six specific actions that\ud
public health units can take which would affect these beliefs, and potentially increase the willingness to disclose\ud
patient information for public health purposes.\ud
Conclusions: The uncertainty surrounding a pandemic of a new strain of influenza has not changed the privacy\ud
concerns of physicians about disclosing patient data. It is important to address these concerns to ensure reliable\ud
reporting during future outbreaks.University of Ottawa Open Access Author Fun
An analytical framework for delirium research in palliative care settings: integrated epidemiologic, clinician-researcher, and knowledge user perspectives
peer-reviewedContext. Delirium often presents difficult management challenges in the context of goals of care in palliative care settings. Objectives. The aim was to formulate an analytical framework for further research on delirium in palliative care settings, prioritize the associated research questions, discuss the inherent methodological challenges associated with relevant studies, and outline the next steps in a program of delirium research.Methods. We combined multidisciplinary input from delirium researchers and knowledge users at an international delirium study planning meeting, relevant literature searches, focused input of epidemiologic expertise, and a meeting participant and coauthor survey to formulate a conceptual research framework and prioritize research questions.Results. Our proposed framework incorporates three main groups of research questions: the first was predominantly epidemiologic, such as delirium occurrence rates, risk factor evaluation, screening, and diagnosis; the second covers pragmatic management questions; and the third relates to the development of predictive models for delirium outcomes. Based on aggregated survey responses to each research question or domain, the combined modal ratings of "very'' or "extremely'' important confirmed their priority.Conclusion. Using an analytical framework to represent the full clinical care pathway of delirium in palliative care settings, we identified multiple knowledge gaps in relation to the occurrence rates, assessment, management, and outcome prediction of delirium in this population. The knowledge synthesis generated from adequately powered, multicenter studies to answer the framework's research questions will inform decision making and policy development regarding delirium detection and management and thus help to achieve better outcomes for patients in palliative care settings. (C) 2014 American Academy of Hospice and Palliative Medicine. Published by Elsevier Inc. All rights reserved.PUBLISHEDpeer-reviewe
Condition Assessment of Power Transformer Onload Tap Changers Using Wavelet Analysis and Self-Organizing Map: Field Evaluation
An onload tap changer (OLTC) is the most maintenance intensive subassembly on a power transformer. Vibration monitoring is an effective technique that can be used to assess the condition of an OLTC nonintrusively. The authors have developed a condition monitoring system for common types of OLTCs that enables the condition of tap changer contacts and associated drive system to be inferred from vibration signals. A number of prototype systems have been installed onto OLTCs in distribution zone substations for field trials. Particular emphasis has been given to the detection of faults in a particular type of older tap changer that had been prone to a range of faults associated with the switching contacts and drive mechanism. For this type of tap changer, it has been shown to be possible to determine not only that the tap changer is aging but also to identify the particular part that is degrading
Characterization of a Severely Degraded Silicone Elastomer HV Insulator - an Aide to Development of Lifetime Assessment Techniques
A high voltage composite insulator showed severe degradation and failure of the silicone elastomer sheds following service in a substation environment. Sensitive analytical techniques were used to investigate the extent of degradation of the silicone elastomer (SiE). The polymer content of some surface regions decreased as degradation increased. This was quantified through observation by scanning electron microscopy (SEM), weight loss upon heating using thermogravimetric analysis (TGA), determination of surface "silica" levels in damaged areas by X-ray photoelectron spectroscopy (XPS) and Raman mapping through a cross-section of the elastomer producing a degradation depth profile. It is believed that due to the environmental conditions at the site of installation, the electric field may have reached corona onset threshold on parts of the elastomer surface. Because of the moist conditions the corona was maintained, effectively preventing the elastomer from regaining hydrophobicity and leading in time to severe degradation. This investigation has also identified techniques applicable to the assessment of condition of other, less damaged SiE insulators which may in turn lead to the prediction of the remaining useful lifetime
Properties of SF6 arcs, free burning arcs, time constants, dielectric recovery and magnetic rotation
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