Τμήμα Ηλεκτρολ. Μηχαν. και Τεχνολ. Υπολογιστών (ΜΔΕ)

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Browsing Τμήμα Ηλεκτρολ. Μηχαν. και Τεχνολ. Υπολογιστών (ΜΔΕ) by Subject "610.28"

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    Design, implementation and evaluation of deconvolution methods in periodic biomedical signals
    Μακρυγιώργου, Δήμητρα; Δερματάς, Ευάγγελος; Δερματάς, Ευάγγελος; Μπερμπερίδης, Κωνσταντίνος; Σκόδρας, Αθανάσιος; Makrygiorgou, Dimitra
    Τμήμα Ηλεκτρολ. Μηχαν. και Τεχνολ. Υπολογιστών (ΜΔΕ)
    In the present thesis, an extensive study and simulation of source separation methods for periodic biosignals are conducted. Biosignals nature and the emerged from their origin and acquisition characteristics make the separation a cumbersome task. A wide variety of source separation techniques have been implemented, each one based on a different assumption, relative to signals characteristics. Methods based on signals correlation, independency, and periodicity are studied. Specifically, fastICA, Infomax, JADE, AMUSE, SOBI, πCA, natural gradient methods and contrast function approaches for convolutive mixture and algorithm based on signal cyclostationarity are simulated and examined on both synthetic data and real biosignals. Finally, an approach, that takes into account the frequency components of the under investigation signals and its inputs are one channel data, is implemented and examined on real biosignals.
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    Development of a new electrospinning setup for reinforced composite nanopolymer scaffolds for orthopedic applications
    Δουλγκέρογλου, Μελέτιος-Νικόλαος; Δεληγιάννη, Δέσποινα; Μαυρίλας, Δημοσθένης; Αθανασίου, Γεώργιος; Doulgkeroglou, Meletios-Nikolaos
    Τμήμα Ηλεκτρολ. Μηχαν. και Τεχνολ. Υπολογιστών (ΜΔΕ)
    During this thesis, we managed to install and establish a functional electrospinning unit in the Laboratory of Biomechanics and Biomedical Engineering in order to test polymers and substances that may be suitable for cellular scaffolds. More specifically, polycaprolactone (PCL) was used as the main polymer either dissolved in acetone or acetic acid 99%. The parameters that affect electrospinning were tested, such as concentration of polymer, distance between the collector and the needle etc and mixtures of polycaprolactone with chitosan and carbon nanotubes were electrospun successfully. For the qualitative evaluation of results, a scanning electron microscopy unit was used with which the architecture of the electrospun materials may be viewed and the diameter size of fibers can be calculated. Polycaprolactone electrospun samples along with samples that contained a blend of polycaprolactone with carbon nanaotubes, were mechanically tested. More specifically, tensile was applied in the specimens and the modulus of elasticity was estimated. Three methods were used for the estimation of the modulus of elasticity while statistical tests were performed in order to examine whether the different methods may be considered equivalent in a confidence level. The three methods contained the estimation of the modulus of elasticity by a regression line in the proportional limit of the specimens in the respective stress-strain curve, by the estimation of a tangent line in a specific point of the linear region and by the secant line that initiates from the start of axis and ends at the end of the linear region. Furthermore, since scaffolds may be considered two dimensional in the macrolevel, a novel method was implemented to create a porous three dimensional scaffold. A new type of a porous collector was designed and implemented based on the design of a commercial screen. Layers of polycaprolactone were electrospun and they were binded with a polymeric glue, leading to the creation of the three dimensional scaffold. The final part of this thesis, included cell cultures in selected materials. The main purpose was to evaluate proliferation and differentiation of the mesenchymal stem cells derived from umbilicar cord. The amount of total protein produced is an indicator of proliferation while the expression of the alkaline phosphatase is an indicator of differentiation of cells into osteoblasts. Cell cultures were observed during the third and seventh day while staining of cell nuclei was performed for visualization of their proliferation.
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    On the modeling protocols of integrated organization and transfer of human biosignals
    Παπαϊωάννου, Μαρία; Λυμπερόπουλος, Δημήτριος; Κωτσόπουλος, Σταύρος; Papaioannou, Maria
    Τμήμα Ηλεκτρολ. Μηχαν. και Τεχνολ. Υπολογιστών (ΜΔΕ)
    Benefits of long-term monitoring have drawn considerable attention in healthcare. Since the acquired data provides an important source of information to clinicians and researchers, the choice for long-term monitoring studies has become frequent. However, long-term monitoring can result in massive datasets, which makes the analysis of the acquired biosignals a challenge. In this case, visualization, which is a key point in signal analysis, presents several limitations and the annotations handling in which some machine learning algorithms depend on, turn out to be a complex task. In order to overcome these problems a novel web-based application for biosignals visualization and annotation in a fast and user friendly way was developed. This was possible through the study and implementation of a visualization model. The main process of this model, the visualization process, comprised the constitution of the domain problem, the abstraction design, the development of a multilevel visualization and the study and choice of the visualization techniques that better communicate the information carried by the data. In a second process, the visual encoding variables were the study target. Finally, the improved interaction exploration techniques were implemented where the annotation handling stands out. Three case projects are presented and discussed, and a usability study supports the reliability of the implemented work.