1,721,000 research outputs found
Optimality, flexibility and efficiency for cell formation in group technology
Full text linkHet onderzoek van Dmitry Krushynskyi concentreert zich op de ontwikkeling van mathematische modellen voor celformatie (CF), die in de praktijk kunnen worden gebruikt om bedrijfsprestaties te verbeteren. Hoewel al meer dan 50 jaar onderzoek is gedaan naar het CF-probleem, baseren de meeste methoden zich op intuïtieve overwegingen en kampen ze onder meer met modellerings- en rekenfouten. Een ander nadeel van de meeste bestaande modellen is hun gebrek aan flexibiliteit: als een model op een ad hoc-procedure is gebaseerd, veroorzaakt elke nieuwe beperking een belangrijke wijziging van het model. In het proefschrift worden twee modellen ontwikkeld.
The thesis focuses on a development of optimal, flexible and efficient models for cell formation (CF) in group technology. By optimality is meant guaranteed quality of the solutions provided by the model, by flexibility - possibility of taking additional constraints and objectives into account, by efficiency - reasonable running times. The main aim is, thus, to provide a reliable tool that can be used by managers to design manufacturing cells based on their own preferences and constraints imposed by a particular manufacturing system.
Though the CF problem has been extensively studied for more than 50 years, there have been very few attempts of solving the problem to optimality and almost all the proposed models for CF problem are either of intuitive (heuristic) nature or are solved by heuristic procedures. This means that the obtained solutions incorporate two types of errors: an intrinsic error of modelling and a computational error induced by a heuristic solution procedure.
The author proposes two models based on the p-Median and the minimum multicut problems, respectively. The first model has very short running times (usually less than 1 sec.) at a cost of a small modelling error. The second approach excludes the modelling error but has substantially larger (yet, practically acceptable) running times. Both models are expressed in terms of Mixed Integer Linear Programs and require a general-purpose MILP solver, like CPLEX or Xpress. Several realistic constraints and objectives, as well as the ways of introducing them into the proposed modes, are discussed.
Lean beyond waste: Towards the reduction of variability and buffers in healthcare
Full text linkIn de zorg is Lean een populaire manier van procesverbetering en het reduceren van verspillingen is een speerpunt in een Lean aanpak. Naast het reduceren van deze verspillingen worden Lean initiatieven ook geacht zich te richten op variabiliteit en de hier uit voortkomende buffers. Er wordt onderscheid gemaakt worden tussen natuurlijke en kunstmatige variabiliteit. Deze kunstmatige variabiliteit komt voort uit ons eigen handelen en moet worden gereduceerd. In een zorgomgeving zijn voornamelijk tijds- en capaciteitsbuffers van toepassing. Naast deze reeds bekende buffervormen is er in dit proefschrift ook uitgebreid aandacht voor een ander buffermechanisme: het bufferen met bewerkingstijd. De resultaten in dit proefschrift dragen bij aan de basis van Lean theorie. In vier onderzoeksprojecten richten we ons op de rollen van variabiliteit en buffers, aspecten van Lean volwassenheid. Ondanks het grote aantal bestudeerde interventies in het eerste onderzoeksprojecten zijn er slechts enkele interventies die aantoonbaar variabiliteit reduceren en doorlooptijd verkorten. Het overgrote deel van de interventies blijkt zich te richten op het reduceren van duidelijke verspillingen. We laten zien dat een relatief kleine kennisbijdrage de focus van de interventies weet te verbreden. Dit proefschrift identificeert meerdere mogelijkheden om Lean in de zorg effectiever toe te passen
Production control for a flexible manufacturing cell
No full texthttp://deepblue.lib.umich.edu/bitstream/2027.42/36118/2/b1723777.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/36118/1/b1723777.0001.001.tx
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Virtual cellular manufacturing : relevance and development of heuristics for family-based dispatching
Full text linkIs it possible to achieve short throughput times in small-batch parts manufacturing operations? Even when a high variety of parts is required, in fluctuating volumes, and with a low to medium annual demand? Virtual Cellular Manufacturing may be one of the answers to the challenges that parts manufacturers face, as the research in this thesis shows.
Virtual cells are groups of resources (e.g. machines, workers), each dedicated to the manufacturing of a part family. These virtual cells help to realise the favourable throughput time performance of conventional manufacturing cells. However, the cells are only formed virtually in the planning and control system. Therefore they can relatively easily be adapted to changed circumstances, without the need for expensive layout changes on the shop floor.
The first part of this thesis focuses on the exploration of the relevant literature on Virtual Cellular Manufacturing. Next, three case studies show the applicability of Virtual Cellular Manufacturing in a practical context. The second part presents three simulation studies of family-based dispatching heuristics (one specific implementation of Virtual Cellular Manufacturing) in basic, but realistic, shop configurations. The results show that family-based dispatching heuristics can achieve significant reductions of throughput times. The findings of this thesis may therefore be relevant to many small-batch discrete parts manufacturing companies.
On the Implementation of Lean Production in Manufacturing SMEs
Full text linkContains fulltext :
282673.pdf (Publisher’s version ) (Open Access)Radboud University, 27 oktober 2022Promotor : Lauche, K. Co-promotores : Schouteten, R.L.J., Slomp, Jannes261 p
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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