1,251 research outputs found
Mean Field Dynamos with Algebraic and Dynamic alpha-Quenchings
Calculations for mean field dynamo models (in both full spheres and spherical
shells), with both algebraic and dynamic --quenchings, show qualitative
as well as quantitative differences and similarities in the dynamical behaviour
of these models. We summarise and enhance recent results with extra examples.
Overall, the effect of using a dynamic appears to be complicated and
is affected by the region of parameter space examined.Comment: 6 pages, 2 postscript figures, also available at
http://www.maths.qmw.ac.uk/~eo
In-process measurements for reactive extrusion monitoring and control
Process monitoring of reactive extrusion is often limited to pressure and temperature measurements at the die. These may be sensitive to fluctuations in the process, but provide limited information on the actual characteristics of the polymer system under manufacture. Consequently, inâprocess measurement using spectroscopic and rheometric techniques, among others, are used to monitor the manufacture of several reactive systems. This approach helps minimize the time lag associated with collecting and preparing samples for measurements offâline, may avoid submitting the sampled material to extra thermal cycles that might change its characteristics, and could support new processâcontrol paradigms. This chapter summarizes the developments of inâline and onâline measuring techniques relevant to reactive extrusion and presents some examples of application
Monitoring of polymer extrusion and compounding processes
This work focuses on monitoring of polymer extrusion and melt
compounding using single or twin-screw extruders. Standard extruder instrumentation
aims at detecting eventual instabilities in flow and heat transfer in the extruder.
Strategies for in-process monitoring considering the actual characteristics of the
material being processed are presented and discussed. On-line and in-line
approaches are defined. The advantages of sampling along the extruder barrel are
demonstrated. Examples of the development and application of in-process optical
spectroscopy and rheometry techniques are presented and discussed
A scaling-up methodology for co-rotating twin-screw extruders
Scaling-up of co-rotating twin screw extruders is studied as a multi-objective optimization
problem where the aim is to define the geometry/operating conditions of the target extruder that
minimize the differences between the values of the performance criteria that depict the reference and
target extruders. Three computational experiments are discussed. These preliminary results seem
encouraging
Use of multi-objective evolutionary algorithms in extrusion scale-up
Extrusion scale-up consists in ensuring identical thermo-mechanical environments in machines of different dimensions, but processing the same material. Given a reference extruder with a certain geometry and operating point, the aim is to define the geometry and operating conditions of a target extruder (of a different magnitude), in order to subject the material being processed to the same flow and heat transfer conditions, thus yielding products with the same characteristics. Scale-up is widely used in industry and academia, for example to extrapolate the results obtained from studies performed in laboratorial machines to the production plant. Since existing scale-up rules are very crude, as they consider a single performance measure and produce unsatisfactory results, this work approaches scale-up as a multi-criteria optimization problem, which seeks to define the geometry/operating conditions of the target extruder that minimize the differences between the values of the criteria for the reference and target extruders. Some case studies are discussed in order to validate the concept
The use of evolutionary algorithms to solve practical problems in polymer extrusion
This work aims at selecting the operating conditions and designing
screws that optimize the performance of single-screw and co-rotating
twin-screw extruders, which are machines widely used by the polymer
processing industry. A special MOEA, denoted as Reduced Pareto Set
Genetic Algorithm, RPSGAe, is presented and used to solve these multiobjective
combinatorial problems. Twin screw design is formulated as a
Travelling Salesman Problem, TSP, given its discrete nature. Various
case studies are analyzed and their validity is discussed, thus demonstrating
the potential practical usefulness of this approach
Polymer extrusion: setting the operating conditions and defining the screw geometry
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RPSGAe - Reduced Pareto Set Genetic Algorithm : application to polymer extrusion
Publicado na serie "Lecture notes in economics and mathematical systems" ; 535In this paper a Multiobjective Optimization Genetic Algorithm,
denoted as Reduced Pareto Set Genetic Algorithm with Elitism
(RPSGAe), is presented and its performance is assessed. The algorithm is
compared with other Evolutionary Multi-Objective Algorithms - EMOAs
(SPEA2, PAES and NSGA-II) using problems from the literature and
statistical comparison techniques. The results obtained showed that the
RPSGAe algorithm has good overall performance. Finally, the RPSGAe
algorithm was applied to the optimization of the polymer extrusion process.
The aim is to implement an automatic optimization scheme capable
of defining the values of important process parameters, such as operating
conditions and screw geometry, yielding the best performance in terms of
prescribed attributes. The results obtained for specific case studies have
physical meaning and correspond to a successful process optimization
EURHEO: the Erasmus Mundus Master in Engineering Rheology
EURHEO (www.eurheo.eu) is a two-year Master course delivered under the prestigious Erasmus Mundus programme. EURHEO aims at offering a pioneer advanced education programme on Rheology and its applications to different Engineering areas. It combines the expertise of six leading European Universities in the field of Rheology (University of Minho (UM - Portugal), the University of Ljubljana (ULJ - Slovenia), the Universidad de Huelva (UHU - Spain), the Kaholieke Universiteit Leuven (KUL - Belgium), the Université catholique de Louvain (UCL - Belgium) and the University of Calabria (UCAL - Italy)) and the syllabus is designed to provide students with the necessary competences to understand the relevance of Rheology in Materials Science and Engineering and apply the knowledge gained in solving real-world Engineering problems both autonomously and included in multidisciplinary research teams.
We will present the EURHEO education programme, and the types of grants that Portuguese and Spanish students can apply for.
The first scientific EURHEO outputs, namely results from selected Master theses, will be presented in 2 posters which report the research carried out by 2 students at UM.European Union and EACEA for granting project 2008-0099-EURHEO: The Erasmus Mundus Master in Engineering Rheology
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