http://ktisis.cut.ac.cy/handle/10488/1039 Search the Channel search http://ktisis.cut.ac.cy/simple-search http://ktisis.cut.ac.cy/handle/10488/7737 Title: The Navigation transformation: point worlds, time abstractions and towards tuning-free navigation<br/><br/>Authors: Loizou, Savvas<br/><br/>Abstract: This paper proposes a novel solution to the navigation problem by mapping an obstacle cluttered environment to a trivial domain called the point world, where the navigation task is reduced to connecting the images of the initial and destination configurations by a straight line. Due to this effect the underlying transformation is termed the Navigation Transformation. The properties of this transformation are studied in this paper as well as its capability to provide a solution to the path and motion planning problems. A construction for such a transformation is proposed. A feedback controller based on the Navigation Transformation is designed that guarantees almost global exponential stability. It is shown that by utilizing the Navigation Transformation, the time for a motion task can be abstracted by means of an appropriately designed time abstracting controller. In addition to the theoretical guarantees, a set of simulation case studies on a star shaped world are provided to demonstrate the effectiveness of the methodology. Fri, 29 Oct 2010 22:58:59 GMT http://ktisis.cut.ac.cy/handle/10488/7633 Title: Sensitivity of hemodynamic parameters to waveform, flow division, and head rotation in the human carotid bifurcation<br/><br/>Authors: Anayiotos, Andreas; Papaharilaou, Yannis; Seimenis, Ioannis<br/><br/>Abstract: Hemodynamic parameters such as time averaged wall shear stress (TAWSS), wall shear stress temporal gradient (WSSTG) and Oscillatory Shear Index (OSI) have previously been cited as parameters associated with the development of atherosclerotic disease at the human carotid bifurcation [1,2]. The sensitivity of these important parameters however, with variations of driving flow waveform, flow division and posture changes are not well known. To investigate these changes, we have used image based CFD, to analyze the flowfield of the carotid bifurcation of a healthy volunteer for five different input waveforms, three flow division ratios and two head postures. Wed, 29 Oct 2008 22:58:59 GMT http://ktisis.cut.ac.cy/handle/10488/7632 Title: Reverse hall-petch effect in ultra nanocrystalline diamond<br/><br/>Authors: Kelires, Pnatelis.C.; Remediakis, Ioannis N.; Kopidakis, Georgios<br/><br/>Abstract: We present atomistic simulations for the mechanical response of ultra nanocrystalline diamond, a polycrystalline form of diamond with grain diameters of the order of a few nm. We consider fully three-dimensional model structures, having several grains of random sizes and orientations, and employ state-of-the-art Monte Carlo simulations. We calculate structural properties, elastic constants and the hardness for this material; our results compare well with experimental observations. Moreover, we verify that this material becomes softer at small grain sizes, in analogy to the observed reversal of the Hall-Petch effect in various nanocrystalline metals. The effect is attributed to the large concentration of grain boundary atoms at smaller grain sizes. Our analysis yields scaling relations for the elastic constants as a function of the average grain size. Wed, 29 Oct 2008 22:58:59 GMT http://ktisis.cut.ac.cy/handle/10488/7593 Title: Neural networks to investigate the effects of smoking and alcohol abuse on the risk for preeclampsia<br/><br/>Authors: Neocleous, Costas; Nikolaides, Kypros H.; Neokleous, Kleanthis C.<br/><br/>Abstract: Following the application of a large number of neural network schemes that have been applied to a large data base of pregnant women, aiming at generating a predictor for the risk of preeclampsia occurrence at an early stage, we investigated the importance of the parameters of smoking and alcohol intake on the classification yield. A number of feedforward neural structures, both standard multilayer and multi-slab, were tried for the prediction. The database was composed of 6838 cases of pregnant women in UK, provided by the Harris Birthright Research Centre for Fetal Medicine in London. For each subject, 24 parameters were measured or recorded. Out of these, 15 parameters were considered as the most influential at characterizing the risk of preeclampsia occurrence, including the characteristics on whether the pregnant woman was an active smoker or not, and on whether she was consuming alcohol. The same data were applied to the same neural architecture, after excluding the information on smoking and alcohol, in order to study the importance of these two parameters on the correct classification yield. It has been found that both information parameters, were needed in order to achieve a correct classification as high as 83.6% of preeclampsia cases in the whole dataset, and of 93.8% in the test set. The preeclampsia cases prediction, for the totally unknown verification test, was 100%. When information on smoking and alcohol intake were not used, the results deteriorated significantly Wed, 29 Oct 2008 22:58:59 GMT