4,550 research outputs found

    Computer Simulation of Particle Suspensions

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    Particle suspensions are ubiquitous in our daily life, but are not well understood due to their complexity. During the last twenty years, various simulation methods have been developed in order to model these systems. Due to varying properties of the solved particles and the solvents, one has to choose the simulation method properly in order to use the available compute resources most effectively with resolving the system as well as needed. Various techniques for the simulation of particle suspensions have been implemented at the Institute for Computational Physics allowing us to study the properties of clay-like systems, where Brownian motion is important, more macroscopic particles like glass spheres or fibers solved in liquids, or even the pneumatic transport of powders in pipes. In this paper we will present the various methods we applied and developed and discuss their individual advantages.Comment: 31 pages, 11 figures, to appear in Lecture Notes in Applied and Computational Mechanics, Springer (2006

    Making a Sustainable Difference to People, Processes and Systems: Whole-Systems Approaches to Process Improvement in Health Systems

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    From Crossref journal articles via Jisc Publications RouterHistory: epub 2023-03-23, issued 2023-03-23Article version: VoRPublication status: PublishedSeán Paul Teeling - ORCID: 0000-0002-4102-7280 https://orcid.org/0000-0002-4102-7280The eighteen papers in this Special Issue, ‘Whole-Systems Approaches to Process Improvement in Health Systems’, address an enduring challenge in healthcare: to improve efficiency with existing or reduced resources, while maintaining safe and effective care [...]pubpu

    Reflection-on-action in qualitative research processes: deconstructing research and developing an honest critical self-appraisal rubric.

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    In this paper, four critical friends meet to discuss qualitative research practices. Together they put one of their own case studies under the knife and deconstruct it to investigate the possibilities that knowledge work is complicated not only by the dynamics of socially constructed enterprises and the actors involved therein, but by the positioning of the researcher. The case describes an evaluative study of a university programme where students engaged in directed experiential learning in group integrated learning settings. The researcher was also the course lead-tutor and this gave rise to some concern, on later reflection and in discussions among critical friends, when issues of researcher positioning were considered. Together, through questioning the topic, the literature, the research experience and the role of the researcher, we developed a reflection-on-action rubric. In a research arena where subjective, interpretative and messy examples abound, as they should, this paper offers an example of our own work, an honest self-appraisal, a rubric for readers’ consideration and a discussion that adds to the perpetual flux of knowledge work

    A Realist Review Protocol into the Contexts and Mechanisms That Enable the Inclusion of Environmental Sustainability Outcomes in the Design of Lean Healthcare Improvement Interventions

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    From Crossref journal articles via Jisc Publications RouterHistory: epub 2024-07-02, issued 2024-07-02Article version: VoRPublication status: PublishedSeán Paul Teeling - ORCID 0000-0002-4102-7280 https://orcid.org/0000-0002-4102-7280Healthcare makes a significant contribution to the social, economic and environmental benefits of communities. It is correspondingly a significant employer and consumer of both energy and consumables, often at high costs. Lean, a quality improvement methodology focuses on the elimination of non-value add (NVA) activities (steps that do not add value from the perspective of the customer) to improve the flow of people, information or goods. Increasingly, Lean thinking is evolving from its initial focus on eliminating NVA to a more holistic approach that encompasses sustainability. However, little work has been undertaken intentionally, including environmental sustainability outcomes in Lean healthcare interventions. Realist review methodology facilitates an understanding of the extent to which an intervention works, for whom, in what context, why and how, and has proven useful in research relating to Lean interventions in healthcare settings. This protocol provides details for a realist review that will enable an understanding of the specific contexts in which certain mechanisms are activated that enable the inclusion of environmental sustainability outcomes in the design of Lean healthcare improvement interventions.pubpu

    The potential, limitations and evaluation of education networks in a monocentric system

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    In almost all education systems, there has been an increasingly incentivised drive to establish and promote local education networks. In the case of Ireland, funded education networks referred to as ‘education clusters’ have been set up to allow schools to collaborate to increase innovation capacity as well as enhance the return on educational investment through economies of scale. While commendable in theory, there is nevertheless, limited evidence relating to the priorities of these networks as perceived by those who are at the core of them, namely teachers. There is also limited research relating to who should be involved in setting evaluation methodologies and standards for the network. As such, using Ireland as a case example, our study was guided by three interconnected questions; what should the priorities of education networks be, what are the benefits and challenges for such priorities and who should be involved in the development of evaluation methodologies and standards?      Findings, many of which we suggest have considerable relevance to most education systems, reveal that, while in theory, although the appeal of education networks in the form of enhanced professional capital is evident, there are still many issues that need to be resolved to enable such networks to deliver on their theoretical possibilities. These include the limitations of reciprocity among network members and the need for facilitated supports to moderate the competitive nature of schools in a network, allowing for competitive collaboration to occur. Importantly, in this research a significant majority of school principals did not see or were not favourable to the idea of education networks being used for cost reductions through economies of scale.En casi todos los sistemas educativos cada vez se incentiva más el interés por establecer y promover redes educativas locales. En el caso de Irlanda, se han establecido redes educati-vas financiadas conocidas como ‘education clusters’ fomentar la colaboración entre centros educativos con el objetivo de mejorar su capacidad innovadora, así como la rentabilidad de la inversión educativa a través de economías de escala. Aunque este enfoque es meritorio en teoría, existen limitadas evidencias acerca de cómo los integrantes de estas redes perciben sus priori-dades. También existen pocas investigaciones sobre quién debería delimitar las metodologías y estándares de evaluación para las redes. Así, nuestro estudio está guiado por tres cuestiones interconectadas, respondidas utilizando el caso irlandés como ejemplo: cuáles deberían ser las prioridades de la red, cuáles son los beneficios y retos de dichas prioridades, y quién debería implicarse en el desarrollo de su evaluación.Los hallazgos revelan que, aunque en teoría los beneficios de las redes educativas relacio-nados con la mejora del capital profesional son evidentes, todavía hay muchas cuestiones que resolver para conseguir que las redes sean capaces de generar dichos beneficios. Estas incluyen las limitaciones de la reciprocidad entre los miembros de las redes y la necesidad de apoyos para moderar la naturaleza competitiva de los centros educativos dentro de una red, permitiendo de esta manera la existencia de una colaboración competitiva. En esta investigación, una mayoría significativa de directores de centro no estaban de acuerdo con la idea de utilizar las redes educativas como un mecanismo de reducción de costes a través de las economías de escala

    An Evaluation of Alumina Supported Platinum Catalysts for the Oxidative Dehydrogenation of n-Butane

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    The oxidative dehydrogenation of n-butane has been studied as a potential alternative to conventional catalytic straight dehydrogenation for the production of butene olefin species. This work was inspired by recent advances in catalytic oxidative dehydrogenation studies utilising short contact times and surface science measurements highlighting the importance of 'hot oxygen' surface chemistry. Two low loading Pt/Al2O3 catalysts have been extensively characterised and used throughout this work. Experimental parameters such as temperature, flow-rate, catalyst mass and hydrocarbon:oxygen ratio were manipulated in an attempt to build a greater understanding of the influential factors responsible for the activity and selectivity of system. The results have shown that catalytic oxidative dehydrogenation is not feasible under the conditions used and that combustion reactions forming carbon dioxide dominate. In contrast, in the absence of the catalyst, relatively high olefin selectivity was observed as a result of homogeneous radical processes. The results from catalytic straight dehydrogenation reactions were dependent on the substrate used. With the 0 65wt% Pt/Al2O3, known from CO chemisorption data to consist of very small platinum crystallites, high dehydrogenation selectivity was observed at modest conversion. Further studies also demonstrated this to be the case regardless of the depth of the catalyst bed. On the contrary, the 0.5wt% Pt/Al2O3 catalyst displayed very poor dehydrogenation selectivity as well as low activity. This was due to the larger platinum crystallites contained in this catalyst, yielding unwanted isomerisation, cracking and hydrogenolysis products, which are known to be structure sensitive favouring larger particle sizes. The low activity observed in the straight dehydrogenation reactions on both catalysts occurred as a result of a combination of carbonaceous blocking of the active sites and pore blocking, restricting access to the active sites. Flow-rate studies demonstrated that the dehydrogenation selectivity could be controlled by manipulation of reactant contact time with the catalyst. Again, the trends were dependent on the substrate used. With the small particles of the 0.65wt% catalyst extended contact times were found to be more favourable for high olefin selectivity, whereas short contact times were found to give the best results for the larger particles of the 0.5wt% catalyst. These observations are consistent with the proposed reaction sequence and the contrasting surface chemistry of the two catalysts, with respect to their particle sizes. On the basis of 'hot oxygen' chemistry, where it was demonstrated that very low concentrations of oxygen could have a profound effect on oxidation reactions involving p-hydrogen abstraction on single crystal surfaces, a study was carried out to see if the dehydrogenation selectivity could be enhanced by manipulation of the hydrocarbon:oxygen ratio. It was found that increasing the oxygen concentration from zero to 1:2 resulted in a dramatic decrease in olefm selectivity with a subsequent increase in butane conversion. It was concluded that the maintenance of a 'hot oxygen' concentration was not possible on the supported catalyst systems studied in a plug flow reactor and that combustion processes were dominant. These combustion reactions being responsible for the increased conversion and decreased selectivity. Pulse-flow measurements were used in order to investigate the initial conditioning of the catalyst surface in an attempt to identify the processes responsible for the effects seen in the continuous-flow (steady state) experiments. A direct correlation was found between the deposition of carbonaceous material on the catalyst surface and the dehydrogenation selectivity. It is observed that the selectivity towards the olefm products increased as carbonaceous material was deposited. It was proposed from this that the presence of the carbonaceous material invoked a change in the electronic nature of the metal surface in a similar manner to that for platinum/tin alloys. The presence of oxygen was found to remove some of the carbonaceous material necessary for olefin formation. In conclusion, the presence of oxygen in the catalytic dehydrogenation of butane using supported platinum catalyst is detrimental to the production of the favoured butene species and that the particle size of the platinum crystallites contained in the catalyst is crucial to obtaining high olefm yields. Dehydrogenation being favoured by small platinum crystals. We also conclude that bridging the gap between single crystal surface science studies and supported catalyst chemistry is not feasible in a microreactor environment operating in steady and non-steady state regimes to achieve the clean, controlled environment compatible with a UHV study

    Dynamics of inelastically colliding rough spheres: Relaxation of translational and rotational energy

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    We study the exchange of kinetic energy between translational and rotational degrees of freedom for inelastic collisions of rough spheres. Even if equipartition holds in the initial state it is immediately destroyed by collisions. The simplest generalisation of the homogeneous cooling state allows for two temperatures, characterizing translational and rotational degrees of freedom separately. For times larger than a crossover frequency, which is determined by the Enskog frequency and the initial temperature, both energies decay algebraically like t2t^{-2} with a fixed ratio of amplitudes, different from one.Comment: 5 pages, RevTeX, 2 eps figures, slightly expanded discussion, new figures with dimensionless units, added references, accepted for publication in PRE as a Rapid Com
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