An unstructured parallel least-squares spectral element solver for incompressible flow problems

The parallelization of the least-squares spectral element formulation of the Stokes problem has recently been discussed for incompressible flow problems on structured grids. In the present work, the extension to unstructured grids is discussed. It will be shown that, to obtain an efficient and scalable method, two different kinds of distribution of data are required involving a rather complicated parallel conversion between the data. Once the data conversion has been performed, a large symmetric positive definite algebraic system has to be solved iteratively. It is well known that the Conjugate Gradient method is a good choice to solve such systems. To improve the convergence rate of the Conjugate Gradient process, both Jacobi and Additive Schwarz preconditioners are applied. The Additive Schwarz preconditioner is based on domain decomposition and can be implemented such that a preconditioning step corresponds to a parallel matrix-by-vector product. The new results reveal that the Additive Schwarz preconditioner is very suitable for the p-refinement version of the least-squares spectral element method. To obtain good portable programs which may run on distributed-memory multiprocessors, networks of workstations as well as shared-memory machines we use MPI (Message Passing Interface). Numerical simulations have been performed to validate the scalability of the different parts of the proposed method. The experiments entailed simulating several large scale incompressible flows on a Cray T3E and on an SGI Origin 3800 with the number of processors varying from one to more than one hundred. The results indicate that the present method has very good parallel scaling properties making it a powerful method for numerical simulations of incompressible flows

Parallel Implementation of a Least-Squares Spectral Element Solver for Incomressible Flow Problems

Least-squares spectral element methods are based on two important and successful numerical methods: spectral/{\em hp} element methods and least-squares finite element methods. Least-squares methods lead to symmetric and positive definite algebraic systems which circumvent the Ladyzhenskaya-Babu\v{s}ka-Brezzi stability condition and consequently allow the use of equal order interpolation polynomials for all variables. In this paper, we present results obtained with a parallel implementation of the least-squares spectral element solver on a distributed memory machine (Cray T3E) and on a virtual shared memory machine (SGI Origin 3800)

A parallel, state-of-the-art, least-squares spectral element solver for incompressible flow problems

The paper deals with the efficient parallelization of least-squares spectral element methods for incompressible flows. The parallelization of this sort of problems requires two different strategies. On the one hand, the spectral element discretization benefits from an element-by-element parallelization strategy. On the other hand, an efficient strategy to solve the large sparse global systems benefits from a row-wise distribution of data. This requires two different kinds of data distributions and the conversion between them is rather complicated. In the present paper, the different strategies together with its conversion are discussed. Moreover, some results obtained on a distributed memory machine (Cray T3E) are presented

Do-Not-Attempt-Resuscitation orders for people with intellectual disabilities : dilemmas and uncertainties for ID physicians and trainees. The importance of the deliberation process

Item does not contain fulltextBACKGROUND: Not much is known about Do-Not-Attempt-Resuscitation (DNAR) decision-making for people with intellectual disabilities (IDs). The aim of this study was to clarify the problems and pitfalls of non-emergency DNAR decision-making for people with IDs, from the perspective of ID physicians. METHODS: This qualitative study was based on semi-structured individual interviews, focus group interviews and an expert meeting, all recorded digitally and transcribed verbatim. Forty ID physicians and trainees were interviewed about problems, pitfalls and dilemmas of DNAR decision-making for people with IDs in the Netherlands. Data were analysed using Grounded Theory procedures. RESULTS: The core category identified was 'Patient-related considerations when issuing DNAR orders'. Within this category, medical considerations were the main contributory factor for the ID physicians. Evaluation of quality of life was left to the relatives and was sometimes a cause of conflicts between physicians and relatives. The category of 'The decision-maker role' was as important as that of 'The decision procedure in an organisational context'. The procedure of issuing a non-emergency DNAR order and the embedding of this procedure in the health care organisation were important for the ID physicians. CONCLUSION: The theory we developed clarifies that DNAR decision-making for people with IDs is complex and causes uncertainties. This theory offers a sound basis for training courses for physicians to deal with uncertainties regarding DNAR decision-making, as well as a method for advance care planning. Health care organisations are strongly advised to implement a procedure regarding DNAR decision-making

A discrete duality finite volume discretization of the vorticity-velocity-pressure formulation of the 2D Stokes problem on almost arbitrary two-dimensional grids

International audienceWe present an application of the discrete duality finite volume method to the numerical approximation of the vorticity-velocity-pressure formulation of the 2D Stokes equations, associated to various non-standard boundary conditions. The finite volume method is based on the use of discrete differential operators obeying some discrete duality principles. The scheme may be seen as an extension of the classical MAC scheme to almost arbitrary meshes, thanks to an appropriate choice of degrees of freedom. The efficiency of the scheme is illustrated by numerical examples over unstructured triangular and locally refined non-conforming meshes, which confirm the theoretical convergence analysis led in the article

On the character and production of ‘active participation’ in neuro-rehabilitation: an Actor-Network perspective

The importance of patients’ active involvement in neuro-rehabilitation after acquired brain injury has been consistently emphasised in recent years. However, most approaches fail to show how ‘active participation’ is practically enacted, focusing on individualised explanations of patient choice and behaviours, or notions of inherent patient traits. Using Actor Network Theory (ANT) as a sensitising concept, we investigated neuro-rehabilitation practices, asking how participation is shaped through biological and socio-material specificities, how rights to knowledge and expertise are constructed, and how a body acclimatises and adjusts within an order of participation and transformation. We analysed video-recorded fieldwork extracts, examining the work of adjusting, testing and transforming; the construction of competence and incompetence; and material and social processes involved in the division of the body and its re-composition. Our findings show how an ANT-sensitised approach provides a critical understanding and context-specific characterisation of ‘active participation’, produced through the association of heterogeneous actors at any one time. Such specificity and the distribution of work suggest that efforts to account for optimum therapy ‘dosages’, and clinical attention to establishing individually-located levels of ‘self-efficacy’ or ‘motivation’ are misdirected. The performance of ‘active participation’, rather, should be re-imagined as a product of diverse, mutually attuned entities

Resilience as a concept for understanding family caregiving of adults with Chronic Obstructive Pulmonary Disease (COPD): an integrative review

Abstract Aims: This paper was a report of the synthesis of evidence on examining the origins and definitions of the concept of resilience, investigating its application in chronic illness management and exploring its utility as a means of understanding family caregiving of adults with Chronic Obstructive Pulmonary Disease. Background: Resilience is a concept that is becoming relevant to understanding how individuals and families live with illness, especially long-term conditions. Caregivers of adults with Chronic Obstructive Pulmonary Disease must be able to respond to exacerbations of the condition and may themselves experience cognitive imbalances. Yet, resilience as a way of understanding family caregiving of adults with COPD is little explored. Design: Literature review – integrative review. Data sources: CINAHL, PubMed, Google Scholar and EBSCO were searched between 1989–2015. Review methods: The principles of rapid evidence assessment were followed. Results: We identified 376 relevant papers: 20 papers reported the presence of the concept of resilience in family caregivers of chronic diseases patients but only 12 papers reported the presence of the concept of resilience in caregivers of Chronic Obstructive Pulmonary Disease patients and have been included in the synthesis. The term resilience in Chronic Obstructive Pulmonary Disease caregiving is most often understood using a deficit model of health

An Unstructured Parallel Least-Squares Spectral Element Solver for Incompressible Flow Problems

The parallelization of the least-squares spectral element formulation of the Stokes problem has recently been discussed for incompressible flow problems on structured grids. In the present work, the extension to unstructured grids is discussed. It will be shown that, to obtain an efficient and scalable method, two different kinds of distribution of data are required involving a rather complicated parallel conversion between the data. Once the data conversion has been performed, a large symmetric positive definite algebraic system has to be solved iteratively. It is well known that the Conjugate Gradient method is a good choice to solve such systems. To improve the convergence rate of the Conjugate Gradient process, both Jacobi and Additive Schwarz preconditioners are applied. The Additive Schwarz preconditioner is based on domain decomposition and can be implemented such that a preconditioning step corresponds to a parallel matrix-by-vector product. The new results reveal that the Additive Schwarz preconditioner is very suitable for the p-refinement version of the least-squares spectral element method. To obtain good portable programs which may run on distributed-memory multiprocessors, networks of workstations as well as shared-memory machines we use MPI (Message Passing Interface). Numerical simulations have been performed to validate the scalability of the different parts of the proposed method. The experiments entailed simulating several large scale incompressible flows on a Cray T3E and on an SGI Origin 3800 with the number of processors varying from one to more than one hundred. The results indicate that the present method has very good parallel scaling properties making it a powerful method for numerical simulations of incompressible flows

The etemic model of Gypsy Roma Traveller community vulnerability: is it time to rethink our understanding of vulnerability?

AIM: To present a new etemic model of vulnerability. BACKGROUND: Despite vulnerability being identified as a core consequence of health and health experiences there has been little research exploring the meaning of vulnerability as a concept. Yet being vulnerable is known to have dire physical/mental health consequences. It is therefore a fundamental issue for nurses to address. To date, the meaning of the term vulnerability has been influenced by the work of Spiers (2000, 2005). Spiers identified two aspects of vulnerability; the etic (external judgment of another persons' vulnerability and the emic (internal lived experience of vulnerability). This approach has led to a plethora of research which has explored the etic (external judgment) of vulnerability and rendered the internal lived (or emic) experience invisible. Consequences of this, for marginalised communities such as Gypsy Roma Travellers include a lack of culturally sensitive services compounding health inequalities. DESIGN: Position paper. METHOD: Drawing upon a qualitative phenomenological research study exploring the lived experience of vulnerability from a Gypsy Roma Travelling community (published previously), this paper presents a new model of vulnerability. This etemic model of vulnerability values both external and internal dimensions of vulnerability and argues for a fusion of these two opposing perspectives. CONCLUSION AND RELEVANCE TO CLINICAL PRACTICE: If nurses and other health and social care professionals wish to develop practice that is successful in engaging with Gypsy Roma Travellers then there is a need to both understand and respect their community. This can be achieved through an etemic approach to understanding their vulnerability achieved by eliciting lived experience alongside the appreciation of epidemiological studies. Doing so would enable the development and delivery of culturally sensitive services facilitating health access to this community. Only then, will their poor health status be successfully addressed. This article is protected by copyright. All rights reserved