A multichannel magnetic probe system for analysing magnetic fluctuations in helical axis plasmas

The need to understand the structure of magnetic fluctuations in H-1NF heliac [S. Hamberger et al., Fusion Technol. 17, 123 (1990)] plasmas has motivated the installation of a sixteen former, tri-axis helical magnetic probe Mirnov array (HMA). The new array complements two existing poloidal Mirnov arrays by providing polarisation information, higher frequency response, and improved toroidal resolution. The helical placement is ideal for helical axis plasmas because it positions the array as close as possible to the plasma in regions of varying degrees of favourable curvature in the magnetohydrodynamic sense, but almost constant magnetic angle. This makes phase variation with probe position near linear, greatly simplifying the analysis of the data. Several of the issues involved in the design, installation, data analysis, and calibration of this unique array are presented including probe coil design, frequency response measurements, mode number identification, orientation calculations, and mapping probe coil positions to magnetic coordinates. Details of specially designed digitally programmable pre-amplifiers, which allow gains and filters to be changed as part of the data acquisition initialisation sequence and stored with the probe signals, are also presented. The low shear heliac geometry [R. Jiménez-Gómez et al., Nucl. Fusion 51, 033001 (2011)], flexibility of the H-1NF heliac, and wealth of information provided by the HMA create a unique opportunity for detailed study of Alfvén eigenmodes, which could be a serious issue for future fusion reactors.This work was supported by the Education Investment Fund under the Super Science Initiative of the Australian Government. S.R.H. wishes to thank AINSE Ltd. for providing financial assistance to enable this work on H-1NF to be conducted

Fast Approximation of Over-Determined Second-Order Linear Boundary Value Problems by Cubic and Quintic Spline Collocation

We present an efficient and generic algorithm for approximating second-order linear boundary value problems through spline collocation. In contrast to the majority of other approaches, our algorithm is designed for over-determined problems. These typically occur in control theory, where a system, e.g., a robot, should be transferred from a certain initial state to a desired target state while respecting characteristic system dynamics. Our method uses polynomials of maximum degree three/five as base functions and generates a cubic/quintic spline, which is C 2 / C 4 continuous and satisfies the underlying ordinary differential equation at user-defined collocation sites. Moreover, the approximation is forced to fulfill an over-determined set of two-point boundary conditions, which are specified by the given control problem. The algorithm is suitable for time-critical applications, where accuracy only plays a secondary role. For consistent boundary conditions, we experimentally validate convergence towards the analytic solution, while for inconsistent boundary conditions our algorithm is still able to find a “reasonable” approximation. However, to avoid divergence, collocation sites have to be appropriately chosen. The proposed scheme is evaluated experimentally through comparison with the analytical solution of a simple test system. Furthermore, a fully documented C++ implementation with unit tests as example applications is provided

Budgetreformen [budgeting reforms]

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The translation and sedimentation of accounting reforms. A comparison of the UK, Austrian and Italian experiences

Since the late 1980s, there has been a significant and progressive movement away from the traditional Public Administration (PA) systems, in favour of NPM-type accounting tools and ideas inspired by the private sector. More recently, a new focus on governance systems, under the banner Public Governance (PG), has emerged. In this paper it is argued that reforms are not isolated events, but are embedded in more global discourses of modernisation and influenced by the institutional pressures present in a certain field at certain points in time. Using extensive document analysis in three countries with different administrative regimes (the UK, Italy and Austria), we examine public sector accounting and budgeting reforms and the underlying discourses put forward in order to support the change. We investigate the extent to which the actual content of the reforms and the discourses they are embedded within are connected over time; that is, whether, and to what degree, the reform “talk” matches the “decisions”. The research shows that in both the UK and in Italy there is consistency between the debates and the decided changes, although the dominant discourse in each country differs, while in Austria changes are decided gradually, and only after they have been announced well in advance in the political debate. We find that in all three countries the new ideas and concepts layer and sediment above the existing ones, rather than replace them. Although all three countries underwent similar accounting and budgeting reforms and relied on similar institutional discourses, each made its own specific translation of the ideas and concepts and is characterised by a specific formation of sedimentations. In addition, the findings suggest that, at present in the three countries, the PG discourse is used to supplement, rather than supplant, other prevailing discourses