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1

The effect of particulate fillers on hardness of polymer composite

Dulebova L., Garbacz T.

Advances in Science and Technology. Research Journal

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2017

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Vol. 11, no 3

66--71

EN

The analysis of polymeric composites can be quite challenging because the samples are often of complex nature due to the presence of various groups of additives, compounding ingredients, and fillers. In this contribution, changes of hardness of Polypropylene (PP) composites during and after the exposure of materials to UV chamber and low temperatures were investigated. The particulate fillers talc and chalk in weight fraction from 10 to 50% and montmorillonite (MMT) in weight fraction 4% were used as fillers in the polypropylene matrix. The composites were mixed in the extruder while the length, diameter of screw, as well as the number of grooves in the feed zone were changed. The influence of ageing – UV radiation and low temperature was examined by change of Shore hardness after 360h and 720h of exposure. According to the performed tests we can conclude that the tested materials may be exposed to UV radiation and low temperature of -20ºC without significant changes of hardness.

2

Scheduling problems with learning and ageing effects: a survey

Janiak A., Krysiak T., Trela R.

Decision Making in Manufacturing and Services

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2011

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Vol. 5, no. 1-2

19-36

EN

In recent years, many papers concerning scheduling problems with simultaneous learning and ageing effects were published. In this paper, the state of the art of research concerning these problems is presented. In order to facilitate understanding this subject, the scheduling problems where these effects occur separately, are firstly explained. Then, the papers devoted to scheduling problems combining the effects of learning and ageing are discussed. Particular attention was paid on practical applications of the considered scheduling problems. After thorough analysis it turned out that both scheduling problems with learning effect, and with ageing effect, as well as, in particular, the problems with models merging learning and ageing effects do not have any reasonable real-life applications. This is because the learning and ageing effects are in general long time horizon phenomena observed in repetitive systems and scheduling theory concerns either with repetitive short-horizon planning problems or single long-horizon projects. Therefore, there is no sense to continue research considering these scheduling problems from practical (computer engineering, automatic control, technical and economical) point of view, unless such reasonable real-life example appears.

3

Scheduling jobs with linear model of simultaneous ageing and learning effects

Janiak A., Lichtenstein M., Rusoń A.

Decision Making in Manufacturing and Services

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2011

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Vol. 5, no. 1-2

37-48

EN

In the paper, we introduce some new scheduling model in which learning and aging effects are both considered simultaneously. In this model the actual processing time of the jobs depends only on its position in a schedule and can be described by the piecewise linear function. For single-processor problem with introduced model, we show that the problem of minimizing the makespan criterion for independent jobs with release dates is strongly NP-hard, but some special cases of this problem are polynomially solvable. Based on those special cases, we propose 4 heuristic algorithms and we experimentally examine their usefulness for solving the general problem.