679 research outputs found

    Norms, legitimacy and institutional independence: the active role of the European Court of Auditors in setting international standards

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    Abstract The European Court of Auditors (ECA), established in 1977, is the external auditor of the EU budget. It was given full EU institutional status in 1993. The Treaty of Amsterdam reaffirmed its independence and extended its audit powers. Based in Luxembourg, it employs around 900 people, of whom less than half are auditors. The ECA is meant to carry out its audit tasks in close cooperation with the supreme audit institutions (SAIs) at the national level. Through its work, it shapes and adopts new audit standards that guide its practice. It is member of International Organisation of Supreme Audit Institutions (INTOSAI) (1953), a forum that brings together professional and technical experts worldwide through working groups and task forces. Drawing on Oliver Buntrock’s notion of ‘micro-institutionalisation’, this article examines how and why the ECA formally engages in standard-setting at the international level. Drawing on primary documents and interviews, it analyses socialization processes and considers motives for participation. The article argues that membership of INTOSAI has helped bolster the ECA’s professional and technical legitimacy over 20 years, and reinforced its independence vis-à-vis its main stakeholders, the European Parliament and European Commission. The paper contributes to our understanding of how a lesser-known EU body contributes to the evaluation of EU budgetary spending

    Precision grinding for rapid manufacturing of large optics

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    Large scale nuclear fusion and astronomy scientific programmes have increased the demand for large freeform mirrors and lenses. Thousands of one metre class, high quality aspherical optical components are required within the next five to ten years. Current manufacturing process chains production time need to be reduced from hundred hours to ten hours. As part of a new process chain for making large optics, an efficient low damage precision grinding process has been proposed. This grinding process aims to shorten the subsequent manufacturing operations. The BoX R grinding machine, built by Cranfield University, provides a rapid and economic solution for grinding large off-axis aspherical and free-form optical components. This thesis reports the development of a precision grinding process for rapid manufacturing of large optics using this grinding mode. Grinding process targets were; form accuracy of 1 m over 1 metre, surface roughness 150 nm (Ra) and subsurface damage below 5 m. Process time target aims to remove 1 mm thickness of material over a metre in ten hours. Grinding experiments were conducted on a 5 axes Edgetek high speed grinding machine and BoX R grinding machine. The surface characteristics obtained on optical materials (ULE, SiC and Zerodur) are investigated. Grinding machine influence on surface roughness, surface profile, subsurface damage, grinding forces and grinding power are discussed. This precision grinding process was validated on large spherical parts, 400 mm ULE and SiC parts and a 1 m Zerodur hexagonal part. A process time of ten hours was achieved using maximum removal rate of 187.5 mm 3 /s on ULE and Zerodur and 112.5 mm 3 /s on SiC. The subsurface damage distribution is shown to be "process" related and "machine dynamics" related. The research proves that a stiffer grinding machine, BoX, induces low subsurface damage depth in glass and glass ceramic.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

    Grinding processes and their effects on surface integrity

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    The introduction of high performance grinding machines in combination with the latest superabrasive technology has the potential to impact significantly on existing process chains. The aim of the research was to look at both the high and low rate removal grinding processes and their effects on the surface integrity, as a means to exploit the above technologies. A major objective was to determine the feasibility of High Efficiency Deep Grinding (HEDG) in cylindrical plunge grinding. HEDG is a high speed removal process which differs from conventional forms of grinding in that it uses large depths of cut together with high feedrates. Together, these changes affect the thermal energy partitioning within the work zone. Through this work an understanding of the process conditions enabled the development of this process, such that prevention of thermal damage to the finished workpiece surface is achievable. At the opposite extreme to the high material removal rates of HEDG, kvdrk was carried out in the high precision finish grinding regime. Developments *ere undertaken to look at the implementation of a modified path into the normal cylindrical plunge grinding action, in a process referred to as Superfinish Grinding. The aim of this process being to demonstrate an improvement to the surface texture primarily through a reduction in grinding directionality. Surface integrity is an important consideration in the development of any grinding process. Damage as a result of grinding is predominately of a thermal nature and results in changes to the material properties in the near surface region. One such change is the residual stress, which was measured using Barkhausen Noise intensity instrumentation, which provided a reliable early indication to a build up in thermal energy. Developments in thermal modelling supported by temperature measurements provided a better understanding of the HEDG regime. The model employed new energy partitioning theories together with circular arc modelling of conditions along the contact length. A model was derived to predict the surface finish produced with the Superfinish Grinding approach, this again provided an increased understanding of the grinding process. Industrial trials have shown how HEDG can be implemented on standard production machine tools for the cylindrical plunge grinding of crankshaft components. The process demonstrated the potential for improved surface integrity, whilst maintaining surface finish and form accuracy. The same grinding machine was also used to generate high quality surfaces using a Superfinish Grinding process. Roughness values of the order of 0.11um RQ were routinely obtained exhibiting reduced levels of grinding directionality. Thus, using a single machine tool and a single set-up, exceptionally high stock removal rates are achievable in a roughing cycle followed by superfinishing to generate the required surface characteristics and profile.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

    Elid superfinishing of spherical bearings

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    Driven by a requirement to extend the lifespan of self-aligning lined spherical bearings, this research investigates the use of Elid (electrolytic in-process dressing) as a method of improving ball surface finish. Elid is a continuous and self-regulating electrochemical dressing process that modifies the surface of a grinding, lapping, or superfinishing wheel. It provides improved grit protrusion, impedes wheel loading / glazing and promotes effective cutting. The characteristics of the newly-developed Elid superfinishing process are in many ways fundamentally different to conventional superfinishing. The main difference is that the use of super-abrasives prevents the wheel from self-sharpening; the normal mechanism by which dulled conventional abrasives are removed and a wheel’s surface refreshed. Because the wheel’s performance and condition is continually maintained inprocess by the Elid system, metal resin bonded (MRB) wheels containing very small super-abrasives can be used. It is the utilization of these fine abrasives (30 to 0.12 μm) that enables surface roughness values below 5 nm Ra to be consistently produced on the spherical surface of corrosion-resistant steel balls. This research provides an in-depth understanding of the Elid spherical superfinishing process; investigating the most effective use of the Elid system, wheel dressing requirements and process performance. Optimisation is provided in terms of evaluating the critical operating parameters, the most effective superfinishing cycle and the implications to the complete ball production chain. A range of techniques are used to evaluate processing performance and ball output quality. These include in-process monitoring of Elid and wheel spindle power levels, analysis of wheel condition, rates of ball surface generation and material removal, ball finish and form. Although predominantly concentrated on corrosion-resistant steel, testing is also conducted on titanium and various ball coatings. In investigating various ways of using the Elid system, this work considers electrodischarge truing, pre-process dressing, Elid 1, Elid 2, Elid 3, and Elid combined with electrolytically assisted superfinishing. The initial process solution of Elid 3 (electrodeless) superfinishing provides the capability of working on all standard size balls, however the dressing system lacks stability. The development of a fixturing system that has a small separate electrode enables Elid 1 (conventional) to be used on the majority of ball sizes. Elid 1 allows more aggressive and consistent dressing, a faster rate of ball material removal and thus a substantially reduced processing time. Results with a #12,000 wheel show that surface quality is vastly improved through the use of Elid whilst maintaining current production standards of form accuracy. Surface finishes of 2nm Ra are achieved, which is an order of magnitude better than balls currently produced using barrelling / polishing. Processing times are equivalent or faster when using Elid 1. Alternatively, consistently sub 10 nm Ra finishes can be reached with a #2,000 wheel using Elid 2 (interval dressing). Generally MRB-CBN wheels provide a more effective carbide cutting action than conventional superfinishing wheels. Controlling wheel condition and achieving full and even ball to wheel conformity are the two most significant contributory factors to the success of Elid spherical superfinishing. Insufficient control of these factors results in poor output quality. Monitoring of wheel spindle and Elid power usage provides useful information in assessing the condition of the wheel and identifying potential problems. High spindle power correlates with fast material removal and is a result of high loads and a free cutting action. Elid processing can be employed for improving surface finish after the conventional honing stage, or after cylindrical grinding for improving both ball form and finish.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

    Galactic S Stars: Investigations of Color, Motion, and Spectral Features

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    Known bright S stars, recognized as such by their enhanced s-process abundances and C/O ratio, are typically members of the asymptotic giant branch (AGB) or the red giant branch (RGB). Few modern digital spectra for these objects have been published, from which intermediate resolution spectral indices and classifications could be derived. For published S stars we find accurate positions using the Two-Micron All Sky Survey (2MASS), and use the FAST spectrograph of the Tillinghast reflector on Mt. Hopkins to obtain the spectra of 57 objects. We make available a digital S star spectral atlas consisting of 14 spectra of S stars with diverse spectral features. We define and derive basic spectral indices that can help distinguish S stars from late-type (M) giants and carbon stars. We convolve all our spectra with the SDSS bandpasses, and employ the resulting gri magnitudes together with 2MASS JHK mags to investigate S star colors. S stars have colors similar to carbon and M stars, and are therefore difficult to distinguish by color alone. Using near and mid-infrared colors from IRAS and AKARI, we identify some of the stars as intrinsic (AGB) or extrinsic (with abundances enhanced by past mass-transfer). We also use V band and 2MASS magnitudes to calculate a temperature index for stars in the sample. We analyze the proper motions and parallaxes of our sample stars to determine upper and lower limit absolute magnitudes and distances, and confirm that most are probably giants.Comment: 11 pages. Accepted for publication in ApJS July 19, 2011. Spectra available as http://hea-www.harvard.edu/~pgreen/SStarAtlas.ta

    Neutron Correlations in the Decay of the First Excited State of 11Li

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    The decay of unbound excited 11Li was measured after being populated by a two-proton removal from a 13B beam at 71 MeV/nucleon. Decay energy spectra and Jacobi plots were obtained from measurements of the momentum vectors of the 9Li fragment and neutrons. A resonance at an excitation energy of ∼1.2 MeV was observed. The kinematics of the decay are equally well fit by a simple dineutron-like model or a phase-space model that includes final state interactions. A sequential decay model can be excluded

    Inference with interference between units in an fMRI experiment of motor inhibition

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    An experimental unit is an opportunity to randomly apply or withhold a treatment. There is interference between units if the application of the treatment to one unit may also affect other units. In cognitive neuroscience, a common form of experiment presents a sequence of stimuli or requests for cognitive activity at random to each experimental subject and measures biological aspects of brain activity that follow these requests. Each subject is then many experimental units, and interference between units within an experimental subject is likely, in part because the stimuli follow one another quickly and in part because human subjects learn or become experienced or primed or bored as the experiment proceeds. We use a recent fMRI experiment concerned with the inhibition of motor activity to illustrate and further develop recently proposed methodology for inference in the presence of interference. A simulation evaluates the power of competing procedures.Comment: Published by Journal of the American Statistical Association at http://www.tandfonline.com/doi/full/10.1080/01621459.2012.655954 . R package cin (Causal Inference for Neuroscience) implementing the proposed method is freely available on CRAN at https://CRAN.R-project.org/package=ci

    Early emergence of CD19-negative human antibody secreting cells at the plasmablast to plasma cell transition

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    Long-lived human plasma cells (PCs) play central roles in immunity and autoimmunity and are enriched amongst the subpopulation of CD19-negative human PCs. However, whether human CD19-negative PCs are necessarily ″aged″ cells that have gradually lost CD19 expression is not known. Assessing peripheral blood samples at steady state and during the acute response to influenza vaccination in healthy donors we identify the presence of phenotypic CD19-negative plasmablasts, the proliferative precursor state to mature PCs, and demonstrate by ELISpot that these are antibody-secreting cells (ASCs). During the acute response to influenza vaccination CD19-positive, CD19-low and CD19-negative ASCs secrete vaccine-specific antibody and show linked IGHV repertoires. To address precursor/product relationships we employ in vitro models which mimic both T-dependent and T-independent differentiation finding that the CD19-negative state can be established at the plasmablast to PC transition, that CD19-negative PCs increase as a percentage of surviving PCs in vitro, and that CD19-negative and CD19-positive PCs can be maintained independently. These data provide proof-of-principle for the view that newly generated ASCs can acquire a mature PC phenotype accompanied by loss of CD19 expression at an early stage of differentiation and that ″aging″ is not an obligate requirement for a CD19-negative state to be established
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