The Egyptian Cardiothoracic Surgeon (ECTS - E-Journal)
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Toward large scale parallel computer simulation of viscoelastic fluid flow: A study of benchmark flow problems
No full textFollowed by our previous study, an OpenFOAM-based viscoelastic flow solver has been further validated through simulation of viscoelastic flow past a cylinder. The drag coefficients calculated by the Oldroyd-B model under the creeping flow in a range of Weissenberg (Wi) number are in good agreements with those reported in the literature. Using the linear Phan-Thien Tanner (L-PTT) model, time-dependent two-dimensional simulations of flow past cylinder have been carried out in a range of Wi number and Reynolds (Re) number, and revealed interesting cooperative effects of inertia and elasticity on the structural evolution of the wake behind the cylinder. The details of parallel computing strategy are analysed and discussed. The codes are evaluated for large scale parallel simulation of two-dimensional and three-dimensional contraction flow as well as two-dimensional flow past a cylinder. The key bottlenecks, which affect the scalability of parallel computing, are discussed
On the use of Dynamic Thermal Line Ratings for Improving Operational Tripping Schemes
No full textThe increasing volume of renewable and intermittent generation that is being connected to power systems means that system operators need more advanced dynamic control tools to manage the increase in congestion and the resulting pressure on system constraints. Dynamic thermal line rating (DTLR) is the thermal rating of a transmission line that is calculated in real-time based on online measurements of the loading of the asset and local weather conditions. This dynamic rating will usually be greater than the static rating that is currently used, as the static rating is defined for the worst case scenario. Therefore, using the dynamic rating allows the thermal constraint on a line to be relaxed and the maximum loading increased. An Operational Tripping Scheme (OTS) is a type of System Integrity Protection Scheme (SIPS) that is used to relieve overloads on transmission lines during stressed system conditions by tripping pre-selected generation assets that are connected to the protected lines. . An OTS is used to increase power flow on overhead lines, without building new assets or compromising security, but doing so results in potential generation constraints and higher system risk. This paper presents the novel integration of DTLRs into an existing OTS in order to improve its performance by reducing the likelihood of unnecessary generation tripping due to overly conservative line ratings. This novel OTS affords the system economic benefits, by avoiding unnecessary tripping, and improves system security, by limiting the propagation of disturbed conditions and avoiding unnecessary tripping actions that could initiate dangerous cascading events that might lead to system blackouts. The new scheme is an example of a Wide Area Monitoring, Protection and Control (WAMPAC) application
Experimental and numerical investigations into electrochemical milling
No full textThis paper presents experimental and numerical investigations into electro-chemical (EC) milling of simple features such as slots and pockets. Preliminary experimental investigations into the machining of a slot enabled appropriate process parameters to be selected; these were then used to machine a simple square pocket and finally a pocket with a human-being shaped protrusion. These features were machined with tools having circular and square cross-sections. The pocket with the protrusion was machined with tool paths of zig–zag and contour-parallel type. The experimental results indicated that the machining accuracy depends upon, amongst other things, on the tool shape and process parameters. A boundary element of the EC machining process was used to predict the shape of the pockets and in most cases, the predicted shapes compared favourably with the actual machined features
Reduction of elementary flux mode complexity enables rational metabolic engineering for biotechnological products
No full textH εκπαίδευση στην κοινωνική εργασία την εποχή της κρίσης στην Ελλάδα: εκπαιδεύοντας το ανθρώπινο δυναμικό να καταπολεμήσει τις ανισότητες
No full textSince 2010, Greece has experienced an unprecedented economic and humanitarian crisis, which continues to have tremendous social impact. Austerity measures and policy cuts have included a dis-investment in social work and social care and more recently the abolition of one of the four national Social Work Departments providing qualifying social work education. In this context, this study addresses the following question: how does pre-qualifying social work education in Greece influence students’ ability to manage value tensions in relation to anti-oppressive practice? Using a case study methodology, the research was based in one Social Work Department (subsequently abolished). Data were collected through semi-structured interviews from social work students at two points in their professional education (n=32) and once from academic staff/placement supervisors (n=10). Data were analysed drawing on grounded theory techniques. In this paper only one particular dataset is considered in detail: the attitudes and experiences of final year students. The main findings indicate students’ narrow understandings and individualistic approaches towards oppression, reflecting an urgent need to redefine social work education and practice in Greece according to current social justice concerns. Specifically, social work education needs to give greater weight to a structural perspective on the dynamics of oppression
Ecologies of educational reflexivity and agency – a different way of thinking about equitable educational policies and practices for England and beyond?
No full textThe current UK education policy for Englandemphasis on equity and social mobility focuses on narrowing the educational attainment gap between more and less advantaged groups of young people – an approach that has strong parallels in many Anglophone countries around the world. We argue that these policy and associated practice proscriptions tend to privilege an individualised narrative of agency for young people, teachers and schools more generally. Our paper argues that this individualised approach is highly problematic in that it decontextualizes the complex and real agentic work of young people in schooling, making it difficult to empirically and theoretically account for differences in educational outcome between and within groups of young people. Informed by a social realist perspective, and in particular the work of Margaret Archer, we propose a theoretical model that we suggest provides greater explanatory and predictive power. The model focuses on the way ecologies of development emerge for young people. We suggest that such ecologies reflect different structural and cultural factors and processes, combining in ways that enable and/or constrain young people’s educational reflexivity and agency and their ensuing educational engagement and attainments. We believe that building a typology of such ecologies of educational reflexivity and agency provides improved ways of developing equitable educational policies and practice - ones that relate clearly to the compositional mix of young people in schools and enable the development of interventions that better relate to such ecologies
Politics and Eschatology: Reassessing the Appeal of the “Jewish Indian” Theory in England and New England in the 1650s
No full textThis article examines the “Jewish Indian” theory— which claimed that American Indians were the ten lost tribes of Israel— in 1650s England and New England. The theory found support in England while failing in New England. This difference in reception can be explained by considering its ecclesiological, political, and eschatological implications. Biblical commentators in both England and New England held to a form of “Judeo-Centric” eschatology, which looked for a sudden, miraculous conversion of the Jews and their eventual superiority to Gentile believers. Such beliefs undermined crucial elements of New England ecclesiology when applied to Native Americans. Conversely, the New England Company used the theory in its publications as a fund raising tool in England. These publications impacted upon debates on Jewish readmission to England in the mid-1650s, with New England missionary models suggested as a way of evangelising Jews. This article therefore argues for the importance of understanding eschatological beliefs in local contexts, while demonstrating the way in which such beliefs can be maintained and reoriented in the face of apparent disconfirmation
Day-ahead Prediction and Shaping of Dynamic Responses of the Demand at Bulk Supply Point
No full textModelling, assessment and Sankey diagrams of integrated electricity-heat-gas networks in multi-vector district energy systems
No full textThe widespread use of decentralised multi-energy supply solutions such as gas-fired Combined Heat and Power (CHP), heat pumps, gas boilers, and so forth is more and more increasing the linkages between electricity, heat and gas distribution networks. However, there is currently no model able to model the three networks in an integrated manner and with a suitable level of detail for operational purposes. A multi-temporal simulation model, which has been implemented in a relevant MATLAB-Excel VBA tool, is presented in this paper to carry out integrated analysis of electricity, heat and gas distribution networks, with specific applications to multi-vector district energy systems. The network linkages have been modelled through a multi-vector efficiency matrix specifically developed to map the transformation of final demands into network energy flows while taking into account the inter-network locations of the individual supply technologies. The relevant coupled electrical, heat and gas flow equations have been solved simultaneously using a Newton-Raphson approach. A real case study of a district multi-energy system in the Campus of the University of Manchester illustrates the quantitative use of the model in different scenarios for technical, economic and environmental studies. Sankey diagrams of the energy flows across the networks are also presented to give a visual picture of the multi-energy interactions and losses in the district in different scenarios. The model can be flexibly adapted to generic network topologies and multi-energy supply technologies, and can thus be used for practical operational implementations as well as to inform planning of low carbon multi-vector energy systems
