415 research outputs found
Control aspects of synchronous machines in power systems applications
No full textDevelopments in control design methods for power systems have continually been made during the last ten years, and the present thesis seeks to make its contribution to this pattern of work. In so doing, it develops electrical machine mathematical models on which the subsequent designs are based. The formulations relate specifically to those from which computer programs may be readily developed and particular importance has been attached to the systematic marshalling of plant and network equations for the subsequent and efficient solution by computer methods. Methods of model reduction and state transformation are described and these are used to manipulate the system models into the form appropriate to the regulator design algorithm. The regulator-design algorithm is described in which a systematic numerical technique is used to predetermine the performance criterionJ = C(xtQx + u )dt. The constraints imposed on the system response by the design specification are associated with the movement of the eigenvalue locations to give actual values for the elements of Q. The algorithm described, for the linear single-input system, is based on the sensitivity of the elements of Q to shifts in the eigenvalue locations to produce a performance criterion for improved system stability. The resulting algorithm is applied to the design of an a.c. turbo generator excitation control and is shown to give a system that has advantages over a controller designed using conventional techniques. The thesis is supported by four published papers in which the author of the present thesis is joint author. One reports on the development of the design algorithm and the others deal with computational aspects of control design and its-application to power systems; computer listings are presented in the papers. In addition, the author's work has been presented at two conferences for which published records exist.</p
The Vanguard (Vol. 17, No. 2), Mar 1970
No full textWilliam Stringfellow, attorney, and outstanding lay theologian is a longtime friend of LHRAA. He is the author of A Private and Public Faith, My People Is the Enemy, and Count It All Joy. In 1969, Dr. Stringfellow was presented with the Mind of Christ Award by LHRAA
Erratum: Medication Adherence Reminder System for Virtual Home Assistants: Mixed Methods Evaluation Study (Jmir Form Res (2021)5:7 (E27327) Doi: 10.2196/27327)
No full textIn “Medication Adherence Reminder System for Virtual Home Assistants: Mixed Methods Evaluation Study” (JMIR Form Res 2021;5(7):e27327), three errors were noted. Due to a system error, the name of one author, Cynthia F Corbett, was replaced with the name of another author on the paper, Elizabeth M Combs. In the originally published paper, the order of authors was listed as follows: Elizabeth M Combs, Elizabeth M Combs, Peyton S Chandarana, Isabel Stringfellow, Karen Worthy, Thien Nguyen, Pamela J Wright, Jason M O\u27Kane This has been corrected to: Cynthia F Corbett, Elizabeth M Combs, Peyton S Chandarana, Isabel Stringfellow, Karen Worthy, Thien Nguyen, Pamela J Wright, Jason M O\u27Kane In the originally published paper, the ORCID of author Cynthia F Corbett was incorrectly published as follows: 0000-0002-2254-6958 This has been corrected to: 0000-0003-2706-2116 In the originally published paper, the email of the Corresponding Author was incorrectly published as follows: [email protected] This has been corrected to: [email protected] The correction will appear in the online version of the paper on the JMIR Publications website on January 27, 2022, together with the publication of this correction notice. Because this was made after submission to PubMed, PubMed Central, and other full-text repositories, the corrected article has also been resubmitted to those repositories
Crab antics? Contesting and perpetuating status hierarchies in professional service firms.
No full textArticleThis is a pre-copyedited, author-produced PDF of an article accepted for publication in Journal of Professions and Organization following peer review. The version of record Stringfellow, L. & Thompson, A., Crab antics? Contesting and perpetuating status hierarchies in professional service firms Journal of Professions and Organization first published online June 19, 2014 doi:10.1093/jpo/jou001 is available online at: http://jpo.oxfordjournals.org/content/early/2014/06/19/jpo.jou001The focus of this research is a multi-level theory building exercise that highlights how status hierarchies are perpetuated, contested, and produced in small firm environments. Through eliciting the narratives of the owners of small accounting practices, we aim to explore the specific dynamics of status and to identify how informants come to understand, perpetuate, and change notions of status within their organizational field. We identify macro-theoretical perspectives through the notion of ‘status framing’, which unpacks the professional norms, institutional logics, and marketplace structures that shape industry practice and understanding. Drawing from micro-level perspectives of ‘status sensemaking’, we highlight how industry members create their own status perceptions that effectively legitimize, reinforce, and contradict industry status archetypes. We highlight the ‘crab antic’ nature to these status battles through narratives of ‘status reconciliation’, where informants effectively negotiate macro and micro status hierarchies. We explicate practice through linking the micro and macro realms of experience in small professional practices and identify how status is socially organized within the accounting profession. In doing so, we contribute to the status literature by highlighting that status is not a unified, stable concept, but one that is highly volatile and often undermined by actors vested in perpetuating the status quo
Doublet tracer tests to determine the contaminant flushing properties of a municipal solid waste landfill
No full textThis paper describes a programme of research investigating horizontal fluid flow and solute transport through saturated municipal solid waste (MSW) landfill. The purpose is to inform engineering strategies for future contaminant flushing. Solute transport between injection/abstraction well pairs (doublets) is investigated using three tracers over five separate tests at well separations between 5 m and 20 m. Two inorganic tracers (lithium and bromide) were used, plus the fluorescent dye tracer, rhodamine-WT. There was no evidence for persistent preferential horizons or pathways at the inter-well scale. The time for tracer movement to the abstraction wells varied with well spacing as predicted for a homogeneous isotropic continuum. The time for tracer movement to remote observation wells was also as expected. Mobile porosity was estimated as ~ 0.02 (~ 4% of total porosity). Good fits to the tracer breakthrough data were achieved using a dual-porosity model, with immobile regions characterised by block diffusion timescales in the range of about one to ten years. This implies that diffusional exchanges are likely to be very significant for engineering of whole-site contaminant flushing and possibly rate-limiting.Abbreviationsb, Thickness of saturated zone [mg/L]; bb, Half-width of an immobile block [m]; B, Block Geometry Function (Barker, 1985) [−]; cX, Background-corrected concentration at location X (e.g. X = M for monitoring point) [mg/L]; CA, Concentration in abstraction well [mg/L]; Cb, Background concentration [mg/L]; CI, Concentration in injection well [mg/L]; CM, Concentration at the monitoring point [mg/L]; CP, Concentration at any point within the waste (e.g. at an observation well) [mg/L]; CR, Concentration returned to the injection well [mg/L]; CT, Tracer input concentration [mg/L]; D, Spacing between injection and pumping well [m]; Da, Apparent diffusion coefficient [m2/d]; M, Transfer function for transport through return pipework to monitoring point [−]; P, Point in the waste (defined by horizontal coordinates x, y); q, Darcy velocity [m/d]; Q, Pumping (and injection) flow rate [m3/d]; rw, Well radius [mm]; R(s), Transfer function for transport through return pipework to injection well [−]; s, Laplace variable [d− 1]; sd, Slope of ln(concentration) against time in a dilution test [log(mg/L)/d]; t, Time [d]; ta(ψ), Advection time for a streamtube [d]; tA, Time constant of abstraction well [d]; tb, Time for fastest advection of tracer from injection to abstraction well [d]; tcb, Characteristic diffusion time to/from immobile zone [d]; tcf, Characteristic diffusion time to/from mobile zone [d]; tfd, Time of first detection of tracer [d]; tI, Time constant of injection well [d]; tM, Advection time from abstraction well to monitoring point [d]; tP, Advection time from injection well to point P in waste [d]; tR, Return time from abstraction well to injection well [d]; tT, Duration of tracer input for a top-hat input [d]; T(s), Transfer function for transport from tracer injection point to injection well [−]; W(s), Transfer function for transport through waste; z, Distance along a streamtube [m]; α, Dispersivity [m]; αL, Dispersivity per unit distance of travel, α /z [−]; γ, Specific weight [N/m3]; θ, Total volumetric water content (porosity) [−]; θim, Immobile volumetric water content (porosity) [−]; θm, Mobile volumetric water content (porosity) [−]; ψ, Angle from line joining doublet wells to streamline entering abstraction well [radians
Sorption of Mecoprop by two clay landfill liner materials: Oxford clay and Mercia mudstone
No full text
Transport of mecoprop through Mercia Mudstone and Oxford Clay at the laboratory scale
No full textLaboratory column tests have been carried out to assess the transport behaviour of Mecoprop in Mercia Mudstone clay and Oxford Clay. Artificially consolidated clay samples were compressed in a triaxial cell to stresses representative of those at the base of a landfill. Uniform steady flow was achieved, and there was no evidence of bypass flow in one or more fast streamtubes. Analysis of Mecoprop and Bromide breakthrough curves showed that the transport characteristics were linear (within noise), with no evidence of irreversible sorption. The possibility of dual-porosity or kinetic sorption processes were not conclusively eliminated. Truncated temporal moments allowed estimates of the linear retardation factor for Mecoprop, which were shown to be a lower-bound. Based on modelling, the retardation factor of Mecoprop in Oxford Clay was estimated to be 17.1, compared with 65.4 in batch sorption tests. The mean retardation factor for Mecoprop in Mercia Mudstone was 3.6, whereas the value from batch sorption tests was 10.0. These data confirm that retardation factors calculated from sorption isotherms obtained from batch experiments on disaggregated samples substantially over-estimate the retardation likely to be observed in compacted clay liners; therefore values from batch tests should be used with caution in groundwater risk assessments
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