Shallow Water Bathymetry Mapping from UAV Imagery based on Machine Learning

The determination of accurate bathymetric information is a key element for near offshore activities, hydrological studies such as coastal engineering applications, sedimentary processes, hydrographic surveying as well as archaeological mapping and biological research. UAV imagery processed with Structure from Motion (SfM) and Multi View Stereo (MVS) techniques can provide a low-cost alternative to established shallow seabed mapping techniques offering as well the important visual information. Nevertheless, water refraction poses significant challenges on depth determination. Till now, this problem has been addressed through customized image-based refraction correction algorithms or by modifying the collinearity equation. In this paper, in order to overcome the water refraction errors, we employ machine learning tools that are able to learn the systematic underestimation of the estimated depths. In the proposed approach, based on known depth observations from bathymetric LiDAR surveys, an SVR model was developed able to estimate more accurately the real depths of point clouds derived from SfM-MVS procedures. Experimental results over two test sites along with the performed quantitative validation indicated the high potential of the developed approach.Comment: 8 pages, 9 figure

High-speed, in-band performance measurement instrumentation for next generation IP networks

Facilitating always-on instrumentation of Internet traffic for the purposes of performance measurement is crucial in order to enable accountability of resource usage and automated network control, management and optimisation. This has proven infeasible to date due to the lack of native measurement mechanisms that can form an integral part of the network‟s main forwarding operation. However, Internet Protocol version 6 (IPv6) specification enables the efficient encoding and processing of optional per-packet information as a native part of the network layer, and this constitutes a strong reason for IPv6 to be adopted as the ubiquitous next generation Internet transport. In this paper we present a very high-speed hardware implementation of in-line measurement, a truly native traffic instrumentation mechanism for the next generation Internet, which facilitates performance measurement of the actual data-carrying traffic at small timescales between two points in the network. This system is designed to operate as part of the routers' fast path and to incur an absolutely minimal impact on the network operation even while instrumenting traffic between the edges of very high capacity links. Our results show that the implementation can be easily accommodated by current FPGA technology, and real Internet traffic traces verify that the overhead incurred by instrumenting every packet over a 10 Gb/s operational backbone link carrying a typical workload is indeed negligible

Top-Down Spatial Categorization Signal from Prefrontal to Posterior Parietal Cortex in the Primate

In the present study we characterized the strength and time course of category-selective responses in prefrontal cortex and area 7a of the posterior parietal cortex during a match-to-sample spatial categorization task. A monkey was trained to categorize whether the height of a horizontal sample bar, presented in rectangular frame at one of three vertical locations, was “high” or “low,” depending on whether its position was above or below the frame's midline. After the display of this sample bar, and after a delay, choice bars were sequentially flashed in two locations: at the top and at the bottom of the frame (“choice” epoch). If the monkey timed its response to the display of the choice bar that matched the sample bar, he was rewarded. We found that cells in prefrontal cortex discriminated category early after the initial sample bar was shown, and continued to differentiate “up” from “down” trials throughout the delay and choice periods. In contrast, parietal cells did not differentiate category until the choice period. Therefore, our results support the notion of a top-down categorical signal that originates in prefrontal cortex and that is only represented in parietal cortex when it is necessary to express the categorical decision through a movement

Decoding of path-guided apparent motion from neural ensembles in posterior parietal cortex

We compared quantitatively the psychometric capacity of human subjects to detect path-guided apparent motion (PAM) and the accuracy of cell ensembles in area 7a to code the same type of stimuli. Nine human subjects performed a detection task of PAM. They were instructed to indicate with a key-press whether they perceived a circularly moving object when five stimuli were flashed successively at the vertices of a regular pentagon. The stimuli were presented along a low contrast circular path with one of 33 speeds (150-600°/s). The average psychometric curve revealed that the threshold for PAM detection was 314°/s. The minimum and maximum thresholds for individual subjects were 277° and 378°/s, respectively. In addition, the activity of cells in area 7a that were modulated by the stimulus position in real or apparent motion was used in a multivariate linear regression analysis to recover the stimulus position over time. Real stimulus motion was decoded successfully from neural ensemble activity at all speeds. In contrast, the decoding of PAM was poor at low stimulus speeds but improved markedly above 300°/s: in fact, this was very close to the threshold above for human subjects to perceive continuous stimulus motion in this condition. These results suggest that the posterior parietal cortex is part of a high-level system that is directly involved in the dynamic representation of complex motion. © Springer-Verlag 2004

Anticlastic curvature measurements on unribbed crystal optics for synchrotron radiation

Various methods have been proposed for measuring the distortion in perfect crystals using double-crystal methods. The majority of these methods rely on making comparisons between double-crystal rocking curve measurements under the spatial extent of an extended x-ray beam. Unless the beam is large and parallel (such as at a synchrotron bending magnet), these methods are not easily scalable to large crystals (e.g., crystal focusing elements for synchrotron beamlines) due to the mechanical inaccuracies inherent in moving the various optical components. We present a method based on a scanning source which simplifies the problems in scaling double-crystal methods to large optics. In addition, results using this method are presented on a ribless sagittal focusing Si(111) crystal demonstrating that the anticlastic deviation can be made to be less than {plus_minus}1 s of arc over a 1-cm-long section parallel to the sagittal axis

Βελτιστοποίηση δικτύου άγονης γραμμής

304 σ.Το ελληνικό ακτοπλοϊκό σύστημα χαρακτηρίστηκε για χρόνια από τον παρεμβατισμό και την υπερπροστασία της ελληνικής πολιτείας. Η νησιωτική μορφολογία της χώρας με τα πολλά μικρά και απομακρυσμένα νησιά, κάνει αναγκαία την επιδότηση ορισμένων γραμμών, η εξυπηρέτηση των οποίων κρίνεται ασύμφορη για τους πλοιοκτήτες. Όσο ίσχυαν οι άδειες σκοπιμότητας το κράτος μπορούσε να εξασφαλίζει την σύνδεση των νησιών της άγονης γραμμής σχετικά εύκολα, με την απελευθέρωση όμως της παροχής υπηρεσιών στις θαλάσσιες μεταφορές τα πράγματα άλλαξαν. Οι πλοιοκτήτες στράφηκαν προς τις πιο εμπορικές γραμμές με αποτέλεσμα ο αριθμός και το κόστος των επιδοτούμενων γραμμών να ανέβουν κατακόρυφα και να φτάσουν για το 2009 τις 84 με το κόστος να ξεπερνά τα 36 εκ. ευρώ. Στα πλαίσια αυτής της διπλωματικής εργασίας θα γίνει μία παρουσίαση των χαρακτηριστικών του δικτύου επιδοτούμενων γραμμών όπως το θεσμικό πλαίσιο, η δομή του δικτύου και ο ακτοπλοϊκός στόλος. Θα γίνει μια περιγραφή της διαδικασίας που ακολουθείται για την σύναψη συμβάσεων δημόσιας υπηρεσίας, αλλά και των θεμάτων που προέκυψαν κατά την μετάβαση της ελληνικής ακτοπλοΐας από το καθεστώς του cabotage στο καθεστώς της ελεύθερης αγοράς. Θα αναφερθούμε στα προβλήματα που αντιμετωπίζει ο χώρος αλλά και στις προτάσεις που έχουν γίνει για την καλύτερη εξυπηρέτηση των επιδοτούμενων γραμμών, όπως η «Μελέτη Σκοπιμότητας (Κόστους – Οφέλους) εναλλακτικών λύσεων οργάνωσης του δικτύου ακτοπλοϊκών συνδέσεων ενδοεπικοινωνίας των μικρών νησιών του Αιγαίου» του ΙΜΕΤ και η εφαρμογή του μεταφορικού ισοδύναμου. Το σημαντικότερο μέρος όμως της εργασίας αυτής εξετάζει την δυνατότητα εφαρμογής ενός μαθηματικού μοντέλου για την βελτιστοποίηση των δρομολογίων τις άγονης γραμμής. Για να γίνει αυτό προσεγγίσαμε το ζήτημα της σχεδίασης του δικτύου επιδοτούμενων γραμμών σύμφωνα με το πρόβλημα του πλανόδιου πωλητή (traveling salesman problem TSP). Εξετάσαμε πέντε διαφορετικές περιπτώσεις κυκλικών ακτοπλοϊκών γραμμών για το νησιωτικό σύμπλεγμα των Κυκλάδων. Η πρώτη αφορούσε μια υπάρχουσα γραμμή, δεύτερη μια γραμμή που περιλάμβανε όλα τα νησιά των Κυκλάδων ενώ η τρίτη και η τέταρτη ένα δίκτυο τριών γραμμών με κέντρο την Σύρο και την Πάρο αντίστοιχα. Τέλος η πέμπτη περίπτωση αφορά ένα δίκτυο τριών γραμμών με κέντρο δύο νησιά, την Σύρο και την Πάρο. Φαίνεται ότι η χρήση μαθηματικών μοντέλων για την βελτιστοποίηση ακτοπλοϊκών γραμμών μπορεί να δώσει αξιοποιήσιμα αποτελέσματα. Όμως για την βελτίωση της κατάστασης στις άγονες γραμμές χρειάζεται προσπάθεια για συνεννόηση από όλες τις εμπλεκόμενες πλευρές. Οι ακτοπλοϊκές συγκοινωνίες είναι μάλλον δυσανάλογα ακριβές σε σχέση με τις προσφερόμενες υπηρεσίες, οι λιμενικές υποδομές των νησιών ελλιπείς ενώ ο μέχρι τώρα σχεδιασμός του δικτύου επιδοτούμενων γραμμών κρίνεται αρκετά πρόχειρος.The Greek coastal shipping system was characterized for years by the interventionism and the overprotection of Greek state. The morphology of the country, with a lot of small and isolated islands makes necessary the subsidy of certain lines, the service of which is disadvantageous for the ship-owners. As long as were in effect the cabotage the state could ensure the connection of non-commercial islands relatively easily, but the release of cabotage changed the terms and conditions.. The ship-owners turned to the more profitable lines and as a result the number and the cost of subsidised lines go up vertically and reach for 2009 the 84 with a cost that exceeds 36 mill. euro. In the current thesis are presented the characteristics of the network of subsidised lines, such as the institutional frame, the structure of network and the coastal shipping fleet. There is also a description of the process that is followed for the contracting of conventions of public service and difficulties that appeared at the transition of Greek coastal shipping from cabotage to free market. Finally mention is made of the existing problems in coastal shipping but also of the proposals that have been made for the amelioration of the system. The most important part of this work examines the possibility of application of a mathematic model for the optimisation of maritime network. The question of designing a network was approached through the travelling salesman problem (TSP). We examined five different cases of circular coastal lines for the cluster of Cyclades. First case concerned an existing line, the second case a line that included all the islands of Cyclades while the third and the fourth were networks of three lines with centre Syra and Paros. Finally the fifth case concerns a network of three lines with centre two islands, Syra and Paros. It appears that the use of mathematic models for the optimisation of coastal lines can give exploitable results. However the improvement of the subsidised lines needs efforts from all the involved sides. The freight cost is rather high considering the offered services on board and the harbour infrastructures of islands are insufficient. Furthermore it hasn’t been any serious attempt by the responsible authorities to design a more effective network until now.Αντώνιος Π. Γεωργόπουλο

Cognitive spatial-motor processes--6. Visuomotor memory scanning

Summary. Fourteen human subjects performed in a modified Sternberg memory-scanning task. First, they made a series of 2 6 movements in different directions from a central point towards peripheral lights on a planar working surface ("list trials"). Then, after a warning signal, one of the previous list stimuli, except the last, was presented again ("test trial"). Subjects were instructed to move in the direction of the stimulus which was presented next in sequence in the list. The mean reaction time (RT) in the test trials increased as a linear function of the number of movements, S, in the list: Mean RT (ms)=105+205.8S (2<S<6). This finding suggests that the task involves memory scanning of visuomotor list items

ART – BASED TRAINING METHODS FOR EMPOWERING ADULTS IN THE DIGITAL ERA

Since the dawn of humanity, dancing has been central to life occasions, for celebration, mourning, entertaining or even communicating. Still, it remains a vital practice around the world. With the development of technology, many efforts have been made to adapt specific choreographies and dancing rituals to the modern era, via digital platforms. However, these sequences cannot be construed as realistic when they are viewed through computers, because the actual expressions are lost in the translation. A lot of attempts have been made to provide a solution to this issue, but the most successful are the motion capturing devices and equipment. In this research, we focus on the recording of choreographies, which represent important social concepts, using a Microsoft Kinect sensor as a motion capturing device. Microsoft Kinect is chosen because it is a low-cost device that can deliver adequate results. The outcome of the research is a “handbook” in virtual reality environment, which can be used as an educational tool by anyone. The project aims at being a response to the global need of today’s world for creation of inclusive environments, where socially aware people can peacefully co – exist. The digital handbook can enhance the skills and competences of adult trainers in arts and culture and every participant gets in touch with sensitive concepts and develops social awareness. Inspiration for the project is drawn via social and humanistic values stemming from philosophical, sociological and psychological texts and it is innovative not only for its content but also for the way this is developed