1,765 research outputs found

    Parallel implementation of an optimal two level additive Schwarz preconditioner for the 3-D finite element solution of elliptic partial differential equations

    Get PDF
    This paper presents a description of the extension and parallel implementation of a new two level additive Schwarz (AS) preconditioner for the solution of 3-D elliptic partial differential equations (PDEs). This preconditioner, introduced in Bank et al. (SIAM J. Sci. Comput. 2002; 23: 1818), is based upon the use of a novel form of overlap between the subdomains which makes use of a hierarchy of meshes: with just a single layer of overlapping elements at each level of the hierarchy. The generalization considered here is based upon the restricted AS approach reported in (SIAM J. Sci. Comput. 1999; 21: 792) and the parallel implementation is an extension of work in two dimensions (Concurrency Comput. Practice Experience 2001; 13: 327)

    What is a Firm? A Reply to Jean-Philippe Robé

    Get PDF
    © The Author(s), 2021. Published by Cambridge University Press on behalf of Millennium Economics Ltd. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1017/S1744137421000369In his recent book on 'Property, Power and Politics', Jean-Philippe Robé makes a strong case for the need to understand the legal foundations of modern capitalism. He also insists that it is important to distinguish between firms and corporations. We agree. But Robé criticizes our definition of firms in terms of legally recognized capacities on the grounds that it does not take the distinction seriously enough. He argues that firms are not legally recognized as such, as the law only knows corporations. This argument, which is capable of different interpretations, leads to the bizarre result that corporations are not firms. Using etymological and other evidence, we show that firms are treated as legally constituted business entities in both common parlance and legal discourse. The way the law defines firms and corporations, while the product of a discourse which is in many ways distinct from everyday language, has such profound implications for the way firms operate in practice that no institutional theory of the firm worthy of the name can afford to ignore it.Peer reviewe

    Laser surface alloying of 316L stainless steel coated with a bioactive hydroxyapatite-titanium oxide composite.

    Get PDF
    Laser surface alloying is a powerful technique for improving the mechanical and chemical properties of engineering components. In this study, laser surface irradiation process employed in the surface modification off 316L stainless steel substrate using hydroxyapatite-titanium oxide to provide a composite ceramic layer for the suitability of applying this technology to improve the biocompatibility of medical alloys and implants. Fusion of the metal surface incorporating hydroxyapatite-titania ceramic particles using a 30 W Nd:YAG laser at different laser powers, 40, 50 and 70% power and a scan speed of 40 mm s(-1) was observed to adopt the optimum condition of ceramic deposition. Coatings were evaluated in terms of microstructure, surface morphology, composition biocompatibility using XRD, ATR-FTIR, SEM and EDS. Evaluation of the in vitro bioactivity by soaking the treated metal in SBF for 10 days showed the deposition of biomimetic apatite

    A case study in Green chemistry: Developing replacements for CFCs

    Get PDF
    Chlorofluorocarbons, CFCs, were developed in the late 1920s for use as safe refrigerant alternatives to sulphur dioxide and ammonia. They were welcomed by industry because of their low toxicity, chemical stability, low flammability, low cost and ease of synthesis. They found wide application as refrigerants, blowing agents, propellants and cleaning agents. Over more than 40 years, applications of CFCs expanded into a wide variety of areas, and grew into a multibillion-dollar industry. Unfortunately, CFCs are not ecologically benign. It became increasingly clear that CFCs were responsible for ozone depletion. In the early 1970s the leading manufacturers of CFCs met to discuss the possible environmental impact of their products.This case study uses a problem based learning approach to take students through the development of replacements for CFCs from the 1970s to today. They investigate the background to the CFC problem and consider data that leads to the decision to investigate possible replacements. They must select and design replacement molecules (HFCs), devise syntheses and then consider the challenge to develop the replacements in a socio-economic and political framework. They also consider the problems posed by existing CFCs, the ‘fridge mountain’ and possible disposal and containment alternatives.The case study brings the story up to date with an investigation of the problems now being associated with HFCs and the search for new alternatives. This activity successfully teaches applied and ‘green’ chemistry via a real life context. The chemistry encountered is of an applied/industrial nature and is set in a socioeconomic context. The influence of political pressures is also brought in when appropriate. Because the activity adopts a problem based approach it is also successful in developing a range of transferable skills, particularly problem solving, teamwork plus verbal and written communication

    Introduction to the Douglass C. North Memorial Issue

    Get PDF
    This is the accepted version of the following article: Geoffrey M. Hodgson, ‘Introduction to the Douglass C. North memorial issue’, Journal of Institutional Economics, (early view) 1 December 2016, which has been published in final form at DOI: https://doi.org/10.1017/S1744137416000400 ©Cambridge UniversityPress 2016This introduction considers the highly influential contribution of Douglass C. North to economic history and institutional economics, as it developed from the 1960s until his death in 2015. It sketches the evolution of his arguments concerning the roles of institutions, organizations and human agency. North’s conception of the economic actor became progressively more sophisticated, by acknowledging the role of ideology and adopting insights from cognitive science. Eventually he abandoned the proposition that institutions are generally efficient, to propose instead that sub-optimal institutional forms could persist. A few noted criticisms of North’s work are also considered here, ranging from those which are arguably off the mark, to others that retain some force. The contributions to this memorial issue are outlined at the end of this introduction.Peer reviewe

    Wind speed variability across the UK between 1957 and 2011

    Get PDF
    Using surface data from 57 UK meteorological stations, a national (BADC-57) and regional wind index for the UK has been calculated for the period 1983 to 2011. For a subset of seven stations, an additional national index (BADC-7) has been calculated for the period 1957 to 2011. The indices show an annual variability of 4% over their respective periods corresponding to a variation in typical wind turbine capacity factor of 7%. These indices are compared with indices calculated from other sources, namely: an index generated using a gridded dataset of observed values interpolated across the UK; an index calculated from an area bounding the UK using the ERA-40 reanalysis dataset; indices calculated from bilinear interpolation of the ERA-40 reanalysis dataset to the 57 and seven stations; and another independent UK wind index. The indices show variation in trends with all showing some level of decline with the exception of that generated using the ERA-40 reanalysis dataset averaged over the UK which shows a significant increase. The various indices show varying degrees of agreement with correlation coefficients, after trends are removed, ranging between 0.611-0.979. The effect of changes in site exposure, instrument bias and measuring height were considered for the BADC-7 and BADC-57 indices. The change in instrument measurement height appears to have a significant biasing effect and it is likely that this along with changes in exposure at urban sites have caused the decline in annual wind speeds observed for some of the indices. There does not appear to be evidence for significant changes in large area (mesoscale) surface roughness. The correlation between annual mean wind speeds at the seven surface station sites used to calculate the BADC-7 index is seen to be quite weak indicating very localised variations in inter-annual variability. When regional differences in the index are investigated, it is seen that wind speeds show a very slight decline across the UK in all regions except the south-east, which shows a slight increase. The greatest decrease is seen in the north-west. These changes are in the same direction as the tentative predictions given by climate models for future changes in wind speed across the UK, though the uncertainty is large given the large degree of inter-annual variation
    • …
    corecore