Simulation of the Long Term Behavior of Polymers on the Basis of Short Term Data

The mechanical long term behavior of polymers is usually determined by long term creep experiments up to 10.000 h which are very time and cost consuming. Therefore these data are often not available for the engineer. But even if long term data is available FEA-tools used in industrial practice usually can not sufficiently represent the nonlinear time, temperature and load-dependency of the mechanical long term behaviour. Hence the dimensioning of polymer parts is still a rather difficult engineering task. As a consequence of this, additional time consuming and expensive component tests in combination with several iterations are often necessary to design a polymer part for long term behaviour. This paper develops a method for the modeling of the load and temperature-dependent mechanical behaviour of polymers over a wide time, load and temperature range by means of finite element analysis. The method includes a material model as well as the determination of material parameters to calibrate the model. As a special feature of this method the model is calibrated by using creep data generated from short term experiments. The procedure improves the simulation of the long term behaviour of plastic-components and reduces the experimental effort significantly. The simulation results are finally validated by creep experiments performed on an example part

On conjectures of Hovey-Strickland and Chai

We prove the height two case of a conjecture of Hovey and Strickland that provides a $K(n)$-local analogue of the Hopkins--Smith thick subcategory theorem. Our approach first reduces the general conjecture to a problem in arithmetic geometry posed by Chai. We then use the Gross--Hopkins period map to verify Chai's Hope at height two and all primes. Along the way, we show that the graded commutative ring of completed cooperations for Morava $E$-theory is coherent, and that every finitely generated Morava module can be realized by a $K(n)$-local spectrum as long as $2p-2>n^2+n$. Finally, we deduce consequences of our results for descent of Balmer spectra

The influence of expertise on brain activation of the action observation network during anticipation of tennis and volleyball serves

In many daily activities, and especially in sport, it is necessary to predict the effects of others' actions in order to initiate appropriate responses. Recently, researchers have suggested that the action-observation network (AON) including the cerebellum plays an essential role during such anticipation, particularly in sport expert performers. In the present study, we examined the influence of task-specific expertise on the AON by investigating differences between two expert groups trained in different sports while anticipating action effects. Altogether, 15 tennis and 16 volleyball experts anticipated the direction of observed tennis and volleyball serves while undergoing functional magnetic resonance imaging (fMRI). The expert group in each sport acted as novice controls in the other sport with which they had only little experience. When contrasting anticipation in both expertise conditions with the corresponding untrained sport, a stronger activation of AON areas (SPL, SMA), and particularly of cerebellar structures, was observed. Furthermore, the neural activation within the cerebellum and the SPL was linearly correlated with participant's anticipation performance, irrespective of the specific expertise. For the SPL, this relationship also holds when an expert performs a domain-specific anticipation task. Notably, the stronger activation of the cerebellum as well as of the SMA and the SPL in the expertise conditions suggests that experts rely on their more fine-tuned perceptual-motor representations that have improved during years of training when anticipating the effects of others' actions in their preferred sport. The association of activation within the SPL and the cerebellum with the task achievement suggests that these areas are the predominant brain sites involved in fast motor predictions. The SPL reflects the processing of domain-specific contextual information and the cerebellum the usage of a predictive internal model to solve the anticipation task. © 2014 Balser, Lorey, Pilgramm, Naumann, Kindermann, Stark, Zentgraf, Williams and Munzert

Post-Editorial of "The Multiverse" Special Volume

A succesful series of papers devoted to various aspects of an idea of the Multiverse have been gathered together and presented to the readers. In this post-editorial we briefly challenge the content referring to the main issues dealt with by the Authors. We hope that this will inspire other investigators for designing future tests which could make this very notion of the Multiverse falsifiable

January 30, 1986

https://scholarlycommons.obu.edu/arbn_85-89/1136/thumbnail.jp