Error estimation and adaptive mesh refinement for parallel analysis of shell structures

The formulation and application of element-level, element-independent error indicators is investigated. This research culminates in the development of an error indicator formulation which is derived based on the projection of element deformation onto the intrinsic element displacement modes. The qualifier 'element-level' means that no information from adjacent elements is used for error estimation. This property is ideally suited for obtaining error values and driving adaptive mesh refinements on parallel computers where access to neighboring elements residing on different processors may incur significant overhead. In addition such estimators are insensitive to the presence of physical interfaces and junctures. An error indicator qualifies as 'element-independent' when only visible quantities such as element stiffness and nodal displacements are used to quantify error. Error evaluation at the element level and element independence for the error indicator are highly desired properties for computing error in production-level finite element codes. Four element-level error indicators have been constructed. Two of the indicators are based on variational formulation of the element stiffness and are element-dependent. Their derivations are retained for developmental purposes. The second two indicators mimic and exceed the first two in performance but require no special formulation of the element stiffness mesh refinement which we demonstrate for two dimensional plane stress problems. The parallelizing of substructures and adaptive mesh refinement is discussed and the final error indicator using two-dimensional plane-stress and three-dimensional shell problems is demonstrated

Europe as a multilevel federation

Peer reviewedPublisher PD

Towards a developmental state? Provincial economic policy in South Africa

This paper explores the meaning of the developmental state for spatial economic policy in South Africa. Two main questions are addressed: do provincial governments have a role to play in promoting economic prosperity, and to what extent do current provincial policies possess the attributes of a developmental state? These attributes are defined as the ability to plan longer term, to focus key partners on a common agenda, and to mobilise state resources to build productive capabilities. The paper argues that the developmental state must harness the power of government at every level to ensure that each part of the country develops to its potential. However, current provincial capacity is uneven, and weakest where support is needed most. Many provinces seem to have partial strategies and lack the wherewithal for sustained implementation. Coordination across government appears to be poor. The paper concludes by suggesting ways provincial policies could be strengthened

Contesting European Regions

The research on which this paper is based was conducted under an Economic and Social Research Council (ESRC) Professorial Fellowship [grant number RES-051-27-0302].Peer reviewedPublisher PD

Periodic orbit quantization of a Hamiltonian map on the sphere

In a previous paper we introduced examples of Hamiltonian mappings with phase space structures resembling circle packings. It was shown that a vast number of periodic orbits can be found using special properties. We now use this information to explore the semiclassical quantization of one of these maps.Comment: 23 pages, REVTEX

Is a definitive trial of prehospital continuous positive airway pressure versus standard oxygen therapy for acute respiratory failure indicated? The ACUTE pilot randomised controlled trial

Objectives To determine the feasibility of a large-scale definitive multicentre trial of prehospital continuous positive airway pressure (CPAP) in acute respiratory failure. Design A single-centre, open-label, individual patient randomised, controlled, external pilot trial. Setting A single UK Ambulance Service, between August 2017 and July 2018. Participants Adults with respiratory distress and peripheral oxygen saturations below British Thoracic Society target levels despite controlled oxygen treatment. Interventions Patients were randomised to prehospital CPAP (O-Two system) versus standard oxygen therapy in a 1:1 ratio using simple randomisation. Primary and secondary outcome measures Feasibility outcomes comprised recruitment rate, adherence to allocated treatment, retention and data completeness. The primary clinical outcome was 30-day mortality. Results 77 patients were enrolled (target 120), including 7 cases with a diagnosis where CPAP could be ineffective or harmful. CPAP was fully delivered in 74% (target 75%). There were no major protocol violations. Full data were available for all key outcomes (targets ≥90%). Overall 30-day mortality was 27.3%. Of these deceased patients, 14/21 (68%) either did not have a respiratory condition or had ceiling of treatment decisions implemented excluding hospital non-invasive ventilation and critical care. Conclusions Recruitment rate was below target and feasibility was not demonstrated. Limited compliance with CPAP, and difficulty in identifying patients who could benefit from CPAP, indicate that prehospital CPAP is unlikely to materially reduce mortality. A definitive effectiveness trial of CPAP is therefore not recommended. Trial registration number ISRCTN12048261; Post-results

Intergovernmental Relations in Scotland: what was the SNP effect?

In Scotland, the formation of a minority government in 2007 by the Scottish National Party (SNP) provided the potential for profound changes in intergovernmental relations. This followed eight years of a Scottish Labour-led coalition government characterised by a low-key and informal relationship with the UK Labour government. From 1999 to 2007, discussions were conducted informally and almost entirely through political parties and executives (ministers and civil servants). Although formal mechanisms for negotiation and dispute resolution existed-including the courts, concordats and Joint Ministerial Committees-they were used rarely. The Scottish Executive also played a minimal role in EU policy-making. Yet, an ‘explosive' new era of relations between the Scottish and UK governments did not arrive in tandem with the new era of party incongruence. The aim of this article is to explore these issues by asking two main questions: why were formal mechanisms used so rarely from 1999 to 2007, and what factors produced muted rather than problematic IGR in the third parliamentary session, between 2007 and 2011

Portable 3-D computed tomography system

Through a Cooperative Research and Development Agreement between Los Alamos National Laboratory and HYTEC, Inc., a portable 3-D Computed Tomography (CT) system has been developed that dramatically reduces the overall complexity and time-to-completion for performing CT studies. The system incorporates an amorphous silicon flat-panel detector, coupled motion control and state of the art software to produce high quality CT results. All alignment, image calibration and radiation exposure monitoring is handled in software, thereby, eliminating the need for precise mechanical positioning during setup or a highly stable source of radiation. The image acquisition hardware occupies a minimal 30-inch x 48-inch footprint and is mounted on a portable cart for transportation between multiple X-ray sites. The software is built on the Windows NT/2K operating system for maximum flexibility in today's industry, and offers an unprecedented user interface designed for technicians and operators who have minimal computer training. Multiple reconstruction methods (parallel, fan and cone beam) are provided and can be run in a parallel-processed mode on any number of Windows NT/2K computers to decrease reconstruction time. Visualization software offers 2-D and 3-D viewing including slice animation and volume rendering of entire objects

Scaling and Formulary cross sections for ion-atom impact ionization

The values of ion-atom ionization cross sections are frequently needed for many applications that utilize the propagation of fast ions through matter. When experimental data and theoretical calculations are not available, approximate formulas are frequently used. This paper briefly summarizes the most important theoretical results and approaches to cross section calculations in order to place the discussion in historical perspective and offer a concise introduction to the topic. Based on experimental data and theoretical predictions, a new fit for ionization cross sections is proposed. The range of validity and accuracy of several frequently used approximations (classical trajectory, the Born approximation, and so forth) are discussed using, as examples, the ionization cross sections of hydrogen and helium atoms by various fully stripped ions.Comment: 46 pages, 8 figure