Το αντικείμενο αυτής της διπλωματικής εργασίας είναι η μελέτη των πρωτοκόλλων κωδικοποίησης και μεταφοράς δεδομένων video και ήχου για δικτυακές εφαρμογές με επέκταση στο διαδίκτυο. Στη συγκεκριμένη εργασία δίνεται έμφαση στις εφαρμογές Voice Over IP (VoIP) και στη συμπεριφορά των πακέτων ήχου στο δίκτυο. Στα αρχικά κεφάλαια αναφέρονται οι βασικές αρχιτεκτονικές αποστολής πακέτων καθώς και τα τυποποιημένα πρωτόκολλα μεταφοράς (TCP/UDP) όπως έχουν θεσπιστεί από τους διεθνείς οργανισμούς. Στη συνέχεια γίνεται ανάλυση των βασικότερων κωδικοποιητών ήχου ομιλίας για τηλεπικοινωνιακές εφαρμογές και αξιολόγησή τους. Τέλος αναπτύσσεται πρόγραμμα τεχνολογίας VoIP με τον κωδικοποιητή G.711 και εξετάζεται η συμπεριφορά της στο δίκτυο αλλά και η απόδοσή της.. Για την ανάπτυξη του προγράμματος χρησιμοποιήθηκε η γλώσσα C# για την οποία δίνονται πολλές λεπτομέρειες στο κεφάλαιο 12. Το σύνολο των προγραμμάτων που χρησιμοποιήθηκαν για τα διαγράμματα και την ανάλυση ήχου αναφέρονται επίσης στο ίδιο κεφάλαιο. / -

Accurate, practical, and affordable pose tracking on manually operated C-arm fluoroscopes is a major technical challenge. Conventional tracking methods, such as optical cameras and radiographic fiducials, are hampered by significant shortcomings. Optical cameras are delicate, costly, and have a complex system setup that is easily susceptible to camera obstruction in cluttered operating room. Radiographic fiducials occupy a significant portion of the fluoroscopic imaging space. Using fiducials also requires segmentation that limits clinical use. In this thesis, an alternative form of tracking is proposed to encode the rotational joints of manually operated C-arms using a tilt sensing accelerometer for tracking the C-arm rotational pose. The technique is evaluated by affixing an accelerometer to a full-scale C-arm where a webcam is used as a substitute for X-ray imaging. Ground truth C-arm rotational poses were obtained from the webcam by tracking a checkerboard plate. From these rotational poses, a series of angle and structural correction equations were formulated that can properly relate the accelerometer angle readings to the C-arm rotational pose in real-time and compensate for systematic structural C-arm deformations, such as sagging and bending. Real-time rotational pose tracking of the primary and secondary joint rotations of the C-arm showed an accuracy of 0.5 degrees in the entire range of interest. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2011-01-28 12:07:32.781

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Recent functional neuroimaging research has highlighted the role of the posterior parietal cortex (PPC) during episodic memory retrieval (Vilberg & Rugg, 2007; Vincent et al., 2006; Wagner et al., 2005; Wheeler & Buckner, 2003; Yonelinas et al., 2005). It has been shown that the PPC is active during the retrieval of old information, when subjects incorrectly believe that new information has been encountered before (false alarms), and when retrieval is accompanied by recollection (Wagner et al., 2005). A preliminary positron emission tomography (PET) study suggests that the PPC is also active when retrieval occurs unintentionally or incidentally, prompted by the presence of an old stimulus item. Collectively these studies suggest that activity in the PPC may be driven by familiarity, irrespective of task demands and independent of its veracity. The main goal of this thesis was to explore, with functional magnetic resonance imaging (fMRI), the conditions under which activity in the PPC may be modulated by the familiarity of veridical and perceived memories. Subjects were presented with scene/word pairs that were repeated 1, 3, or 7 times on Day 1. On Day 2, while MRI scans were recorded, subjects studied either, new items, old pairs (same-form) one additional time (2nd,, 4th, or 8th presentation), or pairs in which the word associated with each picture was changed (different-form) one additional time (2nd,, 4th, or 8th presentation). Same form pairs activated bilateral inferior parietal lobule compared to novel pairs replicating the findings from the PET study on incidental retrieval. Same and different form pairs did not differ on amount of parietal activity. Additionally, same form pairs that were repeated 8 times displayed more PPC activity than same form pairs repeated two and four times while there was no difference across different form repetitions. Together these results indicate that items that are old and that those that are new but are perceived as old activate the inferior parietal lobule.

The genome of an organism contains all hereditary information encoded in DNA.Genome databases are rapidly increasing. This increase in the amount of DNA data demands an increasing need to compress the DNA data in less space for faster transmission and research activities. General text compression algorithms don’t utilize the specific characteristics of a DNA sequence. There are various tools developed using different algorithms and approaches. Many of these tools include the implementation of Huffman encoding to incorporate the characteristics of DNA sequences. Huffman-based techniques center on the idea of selecting repeated sequences to form a skewed Huffman tree. The algorithm also lies around constructing multiple Huffman trees when encoding. These implementations have demonstrated an improvement in the compression ratios compared to the standard Huffman tree. This research suggests few improvements over one of these algorithms to select the repeat sequences to obtain better compression ratios.

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