482 research outputs found

    The State-of-the-Art Survey on Optimization Methods for Cyber-physical Networks

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    Cyber-Physical Systems (CPS) are increasingly complex and frequently integrated into modern societies via critical infrastructure systems, products, and services. Consequently, there is a need for reliable functionality of these complex systems under various scenarios, from physical failures due to aging, through to cyber attacks. Indeed, the development of effective strategies to restore disrupted infrastructure systems continues to be a major challenge. Hitherto, there have been an increasing number of papers evaluating cyber-physical infrastructures, yet a comprehensive review focusing on mathematical modeling and different optimization methods is still lacking. Thus, this review paper appraises the literature on optimization techniques for CPS facing disruption, to synthesize key findings on the current methods in this domain. A total of 108 relevant research papers are reviewed following an extensive assessment of all major scientific databases. The main mathematical modeling practices and optimization methods are identified for both deterministic and stochastic formulations, categorizing them based on the solution approach (exact, heuristic, meta-heuristic), objective function, and network size. We also perform keyword clustering and bibliographic coupling analyses to summarize the current research trends. Future research needs in terms of the scalability of optimization algorithms are discussed. Overall, there is a need to shift towards more scalable optimization solution algorithms, empowered by data-driven methods and machine learning, to provide reliable decision-support systems for decision-makers and practitioners

    Exploring the use of data envelopment analysis for evaluation in primary care

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    Primary care is currently at the heart of the National Health Service policy. The newly established organisations, known as Primary Care Groups and Trusts (PCG/Ts), have the crucial role of improving the efficiency and equity in primary care delivery. However, not many studies have focused on performance assessment in primary care provision. In this thesis we aim to contribute to a discussion regarding appropriate ways to compare the performance of primary care providers and the effective ways to use these results in order to improve performance in primary care. Following a review of the literature, a conceptual framework for performance assessment in primary care was developed in collaboration with a sample of PCG/Ts. This framework aims to establish a link between the local needs, the resources used, the services delivered and the outcomes achieved in primary care. Based on the relationships between these elements, four performance assessment criteria were defined: equity, efficiency, service effectiveness and cost effectiveness. DEA is then proposed to measure efficiency, service effectiveness and cost effectiveness, given the fact that it can handle multiple inputs and outputs without requiring the specification of a functional form. Following the Government’s policy of focusing on the management of chronic diseases, this conceptual framework is then applied to compare the performance of a sample of GP surgeries in terms of their delivery of diabetes care. An exploratory and formative comparison is undertaken in order to investigate why certain surgeries appear to perform better than others, and in order to identify ways in which some of the surgeries can improve their performance. The relationships between the different performance criteria are also investigated, together with the ways in which an adequate balance between the different criteria can be achieved. Several conclusions are arrived at and several contributions arc made to this research area. The usefulness of complementing efficiency analysis with equity and effectiveness analysis; the usefulness of following a formative methodology in the use of DEA; the importance of estimating the costs involved in achieving speciality based outcomes; the importance of area deprivation in the achievement of effectiveness and the limitations of the data available in primary care in England

    Stakeholder identification and engagement in problem structuring interventions

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    © 2019 The Authors This paper addresses the under-researched issue of stakeholder identification and engagement in problem structuring interventions. A concise framework is proposed to aid critical reflection in the design and reporting of stakeholder identification and engagement. This is grounded in a critical-systemic epistemology, and is informed by social identity theory. We illustrate the utility of the framework with an example of a problem structuring workshop, which was part of a green innovation project on the development of a technology for the recovery of rare metals from steel slag. The workshop was initially going to be designed to surface stakeholder views on the technology itself. However, it became apparent that a range of other strategic issues concerning the future of the site were going to impact on decision making about the use of steel slag. It therefore became important to evolve the agenda for the problem structuring, and this is where the critical-systemic approach made a difference. It enabled the workshop to be reframed as a community-based event looking at how the former steelworks site could be developed for new purposes. Evaluation of this problem structuring intervention revealed significant stakeholder learning about the issues needing to be accounted for, and a range of possible options for the development of the steelworks site were explored. The paper ends with a discussion of the utility of social identity theory for understanding the processes and outcomes of the workshop, and reflections are provided on its implications for operational research practice more generally

    Health care and social justice evaluation : a critical and pluralist approach

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    This thesis proposes a critical, systemic and pluralist approach to evaluating health programs. It examines ways in which efforts to promote equality and plurality are undermined by the application of foundationalist and universal conceptions of social justice and evaluation. This approach is developed within the current debate taking place in the field of Critical Systems Thinking, particularly in the area of the evaluation of social and health programs.It is argued that the potential for equality and plurality in Western societies goes beyond the questions of economic exploitation, military, cultural and political oppression and encompasses the relation between power and knowledge which is inherent in rationalities governing the formulation, the implementation and the operation of health programs. The thesis offers an alternative view of social justice that conciliates equality with plurality, and promotes these values through an evaluative procedure. Using Foucault's philosophy, it is proposed that a nonfoundationalist conception of social justice should be understood in terms of the interactions between three areas of human activity, namely knowledge, morality, and techniques and technologies of government. As regards the possibilities for developing a non-foundational and non-universal evaluative judgement, the thesis assumes a decentered conception of truth in the analysis of society and morality, and acknowledges the role of power as factor of generalisation or diversification of truth. Thus complexes of power-knowledge-morality are at the centre of our evaluative judgements of social justice. In order to encourage equality and plurality, this thesis proposes a rationale for evaluation that includes three main methodological guidelines: a decentered conception of critique regarding the problems and negative effects of a health program (unfolding in reverse); the promotion of subjectivity (autonomy, diversity, solidarity) through self-knowledge and self-regulation of desires (folding); and participation in the reordering of society through an ethical and political process of decision-making (ethical and political unfolding of the situated truths of the subjects). The processes are designed to interrelate and iterate in a complex way. They should include the exploration, choice and combination of methods and/or their parts, and of the strategic positions in scientific and ethical discursivities by thinking critically and acting in a situated and participative way

    A Polyhedral Study of Mixed 0-1 Set

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    We consider a variant of the well-known single node fixed charge network flow set with constant capacities. This set arises from the relaxation of more general mixed integer sets such as lot-sizing problems with multiple suppliers. We provide a complete polyhedral characterization of the convex hull of the given set

    Characterising and modeling the co-evolution of transportation networks and territories

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    The identification of structuring effects of transportation infrastructure on territorial dynamics remains an open research problem. This issue is one of the aspects of approaches on complexity of territorial dynamics, within which territories and networks would be co-evolving. The aim of this thesis is to challenge this view on interactions between networks and territories, both at the conceptual and empirical level, by integrating them in simulation models of territorial systems.Comment: Doctoral dissertation (2017), Universit\'e Paris 7 Denis Diderot. Translated from French. Several papers compose this PhD thesis; overlap with: arXiv:{1605.08888, 1608.00840, 1608.05266, 1612.08504, 1706.07467, 1706.09244, 1708.06743, 1709.08684, 1712.00805, 1803.11457, 1804.09416, 1804.09430, 1805.05195, 1808.07282, 1809.00861, 1811.04270, 1812.01473, 1812.06008, 1908.02034, 2012.13367, 2102.13501, 2106.11996
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