1,254 research outputs found

    Alternating Projections and Douglas-Rachford for Sparse Affine Feasibility

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    The problem of finding a vector with the fewest nonzero elements that satisfies an underdetermined system of linear equations is an NP-complete problem that is typically solved numerically via convex heuristics or nicely-behaved nonconvex relaxations. In this work we consider elementary methods based on projections for solving a sparse feasibility problem without employing convex heuristics. In a recent paper Bauschke, Luke, Phan and Wang (2014) showed that, locally, the fundamental method of alternating projections must converge linearly to a solution to the sparse feasibility problem with an affine constraint. In this paper we apply different analytical tools that allow us to show global linear convergence of alternating projections under familiar constraint qualifications. These analytical tools can also be applied to other algorithms. This is demonstrated with the prominent Douglas-Rachford algorithm where we establish local linear convergence of this method applied to the sparse affine feasibility problem.Comment: 29 pages, 2 figures, 37 references. Much expanded version from last submission. Title changed to reflect new development

    Indicators for managing human centred manufacturing

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    Establishing indicators for managing human factors (HF) aspects in the design of production systems remains a challenge. We address the problem in two dimensions – firstly, what aspects of HF are to be considered, and secondly, where in the development process HF is to be measured. In these dimensions a large number of HF metrics are possible in the perceptual, cognitive, physical and psychosocial domains of HF. The relevance of these measures to injury, productivity, quality and organizational strategy continue to be poorly understood. From this perspective we make propositions on the need for: 1) strategic HF metrics selection, 2) metrics application throughout the development process, 3) predictive ‘virtual’ HF metrics approaches, 4) metrics based design guidelines, 5) connecting metrics with design choices and strategies, 6) integrating HF metrics within existing approaches, 7) continuous improvement of the metrics system, and 8) the need to evaluate metrics system quality

    Projection Methods in Sparse and Low Rank Feasibility

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    In this thesis, we give an analysis of fixed point algorithms involving projections onto closed, not necessarily convex, subsets of finite dimensional vector spaces. These methods are used in applications such as imaging science, signal processing, and inverse problems. The tools used in the analysis place this work at the intersection of optimization and variational analysis. Based on the underlying optimization problems, this work is devided into two main parts. The first one is the compressed sensing problem. Because the problem is NP-hard, we relax it to a feasibility problem with two sets, namely, the set of vectors with at most s nonzero entries and, for a linear mapping M the affine subspace B of vectors satisfying Mx=p for p given. This problem will be referred to as the sparse-affine-feasibility problem. For the Douglas-Rachford algorithm, we give the proof of linear convergence to a fixed point in the case of a feasibility problem of two affine subspaces. It allows us to conclude a result of local linear convergence of the Douglas-Rachford algorithm in the sparse affine feasibility problem. Proceeding, we name sufficient conditions for the alternating projections algorithm to converge to the intersection of an affine subspace with lower level sets of point symmetric, lower semicontinuous, subadditive functions. This implies convergence of alternating projections to a solution of the sparse affine feasibility problem. Together with a result of local linear convergence of the alternating projections algorithm, this allows us to deduce linear convergence after finitely many steps for any initial point of a sequence of points generated by the alternating projections algorithm. The second part of this dissertation deals with the minimization of the rank of matrices satisfying a set of linear equations. This problem will be called rank-constrained-affine-feasibility problem. The motivation for the analysis of the rank minimization problem comes from the physical application of phase retrieval and a reformulation of the same as a rank minimization problem. We show that, locally, the method of alternating projections must converge at linear rate to a solution of the rank constrained affine feasibility problem

    Human Factors: Spanning the Gap between OM & HRM

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    Purpose: This paper examines the claim that the application of human factors (HF) knowledge can improve both human well-being and operations system performance. Methodology: A systematic review was conducted using a general and two specialist databases to identify empirical studies addressing both human effects and operations system effects in examining manufacturing operations system design aspects. Findings: We found 45 empirical studies addressing both the human effects and system effects of operations system (re)design. Of those studies providing clear directional effects, 95% showed a convergence between human effects and system effects (+,+ or -,-), 5% showed a divergence of human and system effects (+,- or -,+). System effects included quality, productivity, implementation performance of new technologies, and also more ‘intangible’ effects in terms of improved communication and co-operation. Human effects included employee health, attitudes, physical workload, and ‘quality of working life’. Research limitations/im

    Without uniform indicators, firms are unable to deal with work health issues

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    Repetitive strain, stress and burnout go largely unreported, write Cory Searcy, Shane Dixon and Patrick Neuman

    Ergonomics Contributions to Company Strategies

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    Managers usually associate ergonomics with occupational health and safety and related legislation, not with business performance. In many companies, these decision makers seem not to be positively motivated to apply ergonomics for reasons of improving health and safety. In order to strengthen the position of ergonomics and ergonomists in the business and management world, we discuss company strategies and business goals to which ergonomics could contribute. Conceptual models are presented and examples are given to illustrate: 1) the present situation in which ergonomics is not part of regular planning and control cycles in organizations to ensure business performance, and 2) the desired situation in which ergonomics is an integrated part of strategy formulation and implementation. In order to realize the desired situation, considerable changes must take place within the ergonomics research, education and practice community by moving from a health ergonomics paradigm to a business ergonomics paradigm, without losing the health and safety goals

    Mitigating Bias in Organizational Development and Use of Artificial Intelligence

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    We theorize why some artificial intelligence (AI) algorithms unexpectedly treat protected classes unfairly. We hypothesize that mechanisms by which AI assumes agencies, rights, and responsibilities of its stakeholders can affect AI bias by increasing complexity and irreducible uncertainties: e.g., AI’s learning method, anthropomorphism level, stakeholder utility optimization approach, and acquisition mode (make, buy, collaborate). In a sample of 726 agentic AI, we find that unsupervised and hybrid learning methods increase the likelihood of AI bias, whereas “strict” supervised learning reduces it. Highly anthropomorphic AI increases the likelihood of AI bias. Using AI to optimize one stakeholder’s utility increases AI bias risk, whereas jointly optimizing the utilities of multiple stakeholders reduces it. User organizations that co-create AI with developer organizations instead of developing it in-house or acquiring it off-the-shelf reduce AI bias risk. The proposed theory and the findings advance our understanding of responsible development and use of agentic AI

    MBE Growth of Al/InAs and Nb/InAs Superconducting Hybrid Nanowire Structures

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    We report on \textit{in situ} growth of crystalline Al and Nb shells on InAs nanowires. The nanowires are grown on Si(111) substrates by molecular beam epitaxy (MBE) without foreign catalysts in the vapor-solid mode. The metal shells are deposited by electron-beam evaporation in a metal MBE. High quality supercondonductor/semiconductor hybrid structures such as Al/InAs and Nb/InAs are of interest for ongoing research in the fields of gateable Josephson junctions and quantum information related research. Systematic investigations of the deposition parameters suitable for metal shell growth are conducted. In case of Al, the substrate temperature, the growth rate and the shell thickness are considered. The substrate temperature as well as the angle of the impinging deposition flux are explored for Nb shells. The core-shell hybrid structures are characterized by electron microscopy and x-ray spectroscopy. Our results show that the substrate temperature is a crucial parameter in order to enable the deposition of smooth Al layers. Contrary, Nb films are less dependent on substrate temperature but strongly affected by the deposition angle. At a temperature of 200{\deg}C Nb reacts with InAs, dissolving the nanowire crystal. Our investigations result in smooth metal shells exhibiting an impurity and defect free, crystalline superconductor/InAs interface. Additionally, we find that the superconductor crystal structure is not affected by stacking faults present in the InAs nanowires.Comment: 8 pages, 10 figures, 1 tabl

    Forsvarsanskaffelser; unntaksretten etter EØS-avtalen artikkel 123 i lys av EU-direktiv 2009/81/EC

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    I 2009 innførte EU et nytt forsvars- og sikkerhetsdirektiv, direktiv 2009/81/EC. Forsvars- og sikkerhetsdirektivet er basert på det alminnelige innkjøpsdirektivet, direktiv 2004/18/EC, men innfører nye regler som skal være særlig tilpasset Forsvarets behov ved offentlige anskaffelser av materiell og tjenester. Spørsmålet er i hvilken utstrekning EØS-avtalen artikkel 123 kan anvendes etter implementeringen av direktivet i Norge
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