Σχολή Ηλεκτρολόγων Μηχανικών και Μηχανικών Υπολογιστών

Μόνιμο URI για αυτήν την κοινότηταhttps://dspace.library.tuc.gr/handle/123456789/2

Μέχρι και τον Ιούνιο του 2016, η Σχολή Ηλεκτρολόγων Μηχανικών και Μηχανικών Υπολογιστών ονομαζόταν Σχολή Ηλεκτρονικών Μηχανικών και Μηχανικών Υπολογιστών.

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3D photorealistic reconstruction and digital restoration of Neoria, Crete using geodetic measurement and computer graphics techniques
(Technical University of Crete, 2015) Sarri Effrosyni; Σαρρη Ευφροσυνη; Mania Aikaterini; Μανια Αικατερινη; Ragia Lemonia; Ραγια Λεμονια; Christodoulakis Stavros; Χριστοδουλακης Σταυρος
This thesis puts forward a 3D reconstruction methodology applied to a historic building taking advantage of the combined speed, range and accuracy of a total geodetic station. The measurements representing geographical data, produced an accurate and photorealistic geometric mesh of a historic monument named ‘Neoria’. ‘Neoria’ is a Venetian building located by the old harbour at Chania, Crete, Greece. The integration of tacheometry acquisition and computer graphics puts forward an effective framework for the accurate 3D reconstruction of a historical building. The main technical challenge of this work was the production of an accurate 3D mesh based on a sufficient but small number of tacheometry measurements acquired fast and at low-cost. A combination of surface reconstruction and processing methods ensured that a detailed geometric mesh was constructed based on a few points. A fully interactive application based on game engine technologies was developed in regards to the reconstructed monument. The user can visualize and tour the monument and the area around it, as well as manipulating the model. Advanced interactive functionalities are offered to the user in relation to identifying restoration areas and visualizing the outcome of such works. Moreover, the user could visualize the co-ordinates of the points measured, calculate distances at will and navigate the complete 3D mesh of the monument. The goal of this framework is to utilize a small number of acquired data points and present a fully interactive visualization of a georeferenced 3D model.
Advanced fuzzy logic controllers design and evaluation for buildings’ occupants thermal–visual comfort and indoor air quality satisfaction
(Elsevier, 2001) Kolokotsa Dionysia; Κολοκοτσα Διονυσια; Tsiavos D.; Stavrakakis Georgios; Σταυρακακης Γεωργιος; Kalaitzakis Kostas; Καλαϊτζακης Κωστας; Antonidakis E.
The aim of this paper is to present and evaluate control strategies for adjustment and preservation of air quality, thermal and visual comfort for buildings’ occupants while, simultaneously, energy consumption reduction is achieved. Fuzzy PID, fuzzy PD and adaptive fuzzy PD control methods are applied. The inputs to any controller are: the PMV index affecting thermal comfort, the CO2 concentration affecting indoor air quality and the illuminance level affecting visual comfort. The adaptive fuzzy PD controller adapts the inputs and outputs scaling factors and is based on a second order reference model. More specifically, the scaling factors are modified according to a sigmoid type function, in such a way that the measured variable to be as closer as possible to the reference model. The adaptive fuzzy PD controller is compared to a non-adaptive fuzzy PD and to an ON–OFF one. The comparison criteria are the energy required and the controlled variables response. Both, energy consumption and variables responses are improved if the adaptive fuzzy PD type controller is used. The buildings’ response to the control signals has been simulated using MATLAB/SIMULINK.
Automated brain structures segmentation using the mean-shift algorithm
(Πολυτεχνείο Κρήτης, 2010) Μαυριγιαννάκης Κωνσταντίνος
Μη διαθέσιμο
A bayesian personalized recommendation system
(Πολυτεχνείο Κρήτης, 2014) Babas Konstantinos; Μπαμπας Κωνσταντινος; Chalkiadakis Georgios; Χαλκιαδακης Γεωργιος; Lagoudakis Michael; Λαγουδακης Μιχαηλ; Deligiannakis Antonios; Δεληγιαννακης Αντωνιος
In this research, we propose a novel Bayesian approach for personalized recommendations. We succeed in providing recommendations that are entirely personalized, based on a user’s past item “consumptions”, building a representative user model which reflects agent’s corresponding beliefs. Having a set of items, our agent has to select the one which better matches her beliefs about a specific user, in order to recommend it and receive the corresponding reward. In our approach, we model both user preferences and items under recommendation as multivariate Gaussian distributions; and make use of Normal-Inverse Wishart priors to model the recommendation agent beliefs about user types. We interpret user ratings in an innovative way, using them to guide a Bayesian updating process that helps us both capture a user’s current mood, and maintain her overall user type. We produced several variants of our approach, and applied them in the movie recommendations domain, evaluating them on data from the MovieLens dataset. We developed a generic & domain independent system, able to face the scalability challenge and able to capture user preferences (long-term and short-term). Moreover, we dealt with the exploration vs exploitation dilemma in this domain, via the application of various exploration algorithms (e.g., VPI exploration). Ours is a completely personalized approach, which exploits Bayesian Reinforcement Learning in order to recommend an item or a top-N group of items, without the need of ratings prediction. We do not employ a Collaborative Filtering or Content-based or Preference Elicitation technique, but we are still able to provide successful recommendations. Furthermore, we tackle the famous “cold-start” problem via the use of Bayesian and VPI explorations. Our algorithms are shown to be competitive against a state-of-the-art method, which nevertheless requires a minimum set of ratings from various users to provide recommendations --- unlike our entirely personalized approach.
Biochemical analysis on Lab on a Chip
(Technical University of Crete, 2014) Kobotheklas Konstantinos; Κομποθεκλας Κωνσταντινος; Kalaitzakis Kostas; Καλαϊτζακης Κωστας; Balas Costas; Μπαλας Κωστας; Koutroulis Eftychios; Κουτρουλης Ευτυχιος
Emerging issues, modern design trends and future challenges for system design research and design of System-on-a-Chip (SoC), are the focus of semiconductor industry. The architecture of SoC designers consider the overall system performance variably (power, thermal efficiency, production costs, etc. ) in order to present to the market complex and competitive products. With the help of micro-fluidic remarkable is the progress in development of Lab-on-a-Chip (LoC) systems in various fields such as the study of cell biology and disease diagnosis. The micro- biosensors, which are based on LoC systems can incorporate numerous techniques for analysis of biochemical reactions, including analysis based on the image, and techniques for the analysis of genes and proteins of the cell. Medical devices that are already on the market provide significant clinical credibility through immunological tests and Point-of-Care (POC) tests for clinical chemistry. Future applications include complex tests, POC tests with high sensitivity and rather complicated tests, such as nucleic acid tests or the integration of multiple tests in one.
BucDoop: Bottom Up Computation of Iceberg Data Cubes with Hadoop
(Πολυτεχνείο Κρήτης, 2014) Tsakonas Konstantinos; Τσακωνας Κωνσταντινος; Deligiannakis Antonios; Δεληγιαννακης Αντωνιος; Garofalakis Minos; Γαροφαλακης Μινως; Christodoulakis Stavros; Χριστοδουλακης Σταυρος
Big Data analysis has been a key matter during the recent years for the study of various phenomena in various science contexts as well as in business intelligence. Furthermore it appears for good reason to remain in focus for the future. Online Analytical processing methods and Data Cubes need to be further studied in order to reduce time used for efficient data analysis. This study introduces BucDoop, a novel algorithm that exploits the parallelism benefits of Hadoop Map Reduce, for the efficient iceberg data cube creation in reasonable time. BucDoop includes the use of the Bottom Up Computation (BUC) idea in the context of iceberg cube data lattice traversal, managing to reduce the amount of data handled with early pruning architecture and producing the portion of the cube needed for analysis purposes (iceberg problem). Experiments conducted herein present an efficient scalability factor for the creation of the iceberg cube for very big data, by-passing the data explosion and memory constraints problem while using only commodity hardware.
Cache management policies for streaming proxies : the cases of fixed and variable video sizes and collaboration among proxies
(Πολυτεχνείο Κρήτης, 2015) Kyriazis Athanasios; Κυριαζης Αθανασιος; Paterakis Michalis; Πατερακης Μιχαλης; Koutsakis Polychronis; Κουτσακης Πολυχρονης; Bletsas Aggelos; Μπλετσας Αγγελος
The easy access on the Internet, the exponential growth of the Internet traffic and the ever enlarging sizes of files which are transferred over it, often lead to network congestion and significant delays in many applications that require timely data transfer. The most important part of data transfer over the Internet corresponds to media streaming applications which require a large portion of the available bandwidth, while at the same time there is the need of achieving low delays, because the delays in these applications are very annoying to the users and some of them may not be willing to experience them. In order to improve the services provided to the users of these applications, the techniques of video caching and of collaborative caching are used. Video caching embodies proxy servers on the network in order to keep frequently accessed data at locations close to the clients. Collaborative caching uses group of proxies which can collaborate with each other, and achieve better performance than with independent standalone proxies. This Thesis proposes new efficient algorithms for video caching which manage the cache of the proxy servers for video transfer in real time and compares them to existing algorithms. Also, a new effective collaborative scenario is proposed and evaluated. In the first two parts of the Thesis the performance of three existing efficient algorithms in the literature, the Number of Common Clients - Size (NCCS), the Least Recently and Least Frequently Used (LRLFU) and the Least Recently Used (LRU) is evaluated and compared for the cases of fixed and variable video sizes. In each of the first two parts of the Thesis a new cache management algorithm is also designed and proposed, this new algorithm consists of a combination of existing efficient algorithms. In the first part of the Thesis the proposed new algorithm (referred to as the LRLFU_Aggressive) does not perform much better than the existing algorithms, but in the second part the proposed new algorithm (referred to as the LRLFU_Modified) significantly improves the performance of the system in comparison to the existing algorithms. In the cache replacement algorithms we examine a value defined for each video, namely the caching value, which is based on the popularity of the videos, in order to retain in the cache the most popular videos. For each requested video which does not exist into the cache, other videos have to be removed (the ones with the lower caching values) in order for the new video to be cached. The performance metrics we use to evaluate and compare the algorithms in our system are the Video Hit Ratio and the Fraction of the Delayed Starts. In the third part of the Thesis a collaborative scheme of two client communities each associated with one proxy server, is defined and studied. While most of the studies in the area of collaborative proxies use the same cache management algorithm in each proxy and assume that each client community communicates via the corresponding proxy with the same content server, in our collaborative system we have used a different cache management algorithm in each of the two proxies and we assumed that there are two content servers each one associated with one of the client communities. Furthermore, we assumed that each of the client communities communicates via the corresponding proxy only with its corresponding content server. Also, we assumed that there is an overlap between the contents of the two content servers. Each of the two different cache management algorithms used in the collaborative scheme caches different videos in the corresponding proxy, and this helps the overall system performance. From the results of our simulation study we derive important conclusions for the performance of the examined collaborative scheme.
Channel coding and detection for increased range bistatic scatter radio
(Technical University of Crete, 2014) Alevizos Panagiotis; Αλεβιζος Παναγιωτης; Bletsas Aggelos; Μπλετσας Αγγελος; Karystinos Georgios; Καρυστινος Γεωργιος; Deligiannakis Antonios; Δεληγιαννακης Αντωνιος
Scatter radio, i.e communication by means of reflection, has emerged as a potential key-enabling technology for ultra low-cost, large-scale, ubiquitous sensor networking. This work jointly studies noncoherent detection and channel coding for scatter radio networks, with the ultimate goal to further extend communication range, compared to prior art. Specifically, this work focuses on frequency shift keying modulation (FSK) in bistatic scatter radio architectures, where carrier emitter is dislocated from the software defined radio receiver (SDR). FSK is ideal for the power limited regime and allows for simple, frequency division multiple access (FDMA) of simultaneously operating receiver-less sensors. A novel composite hypothesis testing decoding rule is derived for noncoherent channel-encoded FSK, in bistatic scatter radio architectures. Such decoding rule is evaluated with short block length channel codes; the latter offer ultra-low encoding complexity, and thus, they are appropriate for resource-constraint scatter radio sensors. Reed-Muller and BCH codes are studied, due to their strong algebraic structure. It is shown that the proposed decoding scheme achieves high diversity order through interleaving. Extensive simulations under Rician fading scenarios include the impact of carrier frequency offset estimation errors, channel coherence time and interleaving depth. Closed-form performance analysis is also provided. Theoretical analysis for maximum likelihood coherent detection and decoding in on-off keying modulation (OOK) is also presented. Furthermore, experimental measurements are conducted outdoors, with a commodity SDR reader and custom scatter radio sensor. Sensor-to-reader ranges up to 134 meters are experimentally demonstrated with omnidirectional antennas and 13 dBm (20 milliWatt) transmission power. Coded setup offered 10 additional meters range extension compared to the state-of-the-art uncoded noncoherent detection. As a result, this thesis provided a simple solution that could further leverage the adoption of scatter radio in large-scale, ultra low-cost wireless sensor networks
Coherent detection and channel coding for backscatter sensor networks
(Πολυτεχνείο Κρήτης, 2014) Fasarakis-Chilliarnt Nikos; Φασαρακης-Χιλλιαρντ Νικος; Bletsas Aggelos; Μπλετσας Αγγελος; Karystinos Georgios; Καρυστινος Γεωργιος; Deligiannakis Antonios; Δεληγιαννακης Αντωνιος
Combining voice and touch modalities in educational games for preschoolers
(Πολυτεχνείο Κρήτης, 2015) Giannakouras Panagiotis; Γιαννακουρας Παναγιωτης; Mania Aikaterini; Μανια Αικατερινη; Digalakis Vasilis; Διγαλακης Βασιλης; Potamianos Alexandros; Ποταμιανος Αλεξανδρος
Η ραγδαία πρόοδος και εξέλιξη σε όλους τους τομείς της τεχνολογίας στις μέρες μας, κάνει πιο προσιτή την επαφή των ανθρώπων με τους ηλεκτρονικούς υπολογιστές σε όλο και νεαρότερες ηλικίες. Παράλληλα, η πρόοδος της ανάπτυξης λογισμικού με τη μορφή διάφορων εφαρμογών σε επίπεδο υπολογιστή ή ταμπλέτας διευκολύνει πολλές πτυχές της καθημερινότητάς μας και βελτιώνει τον τρόπο και την ποιότητα της ζωής μας. Οι εφαρμογές και ιδιαίτερα αυτές που συνδυάζουν φωνή και αφή (διαδραστικότητα με το χρήστη), έχουν αποδειχθεί ιδιαίτερα ευεργετικά για παιδιά κάθε ηλικίας από προσχολική μέχρι και έφηβους. Στην εργασία αυτή, αρχικά, γίνεται μια σύντομη αναφορά στο θεωρητικό πλαίσιο που βασίζεται η εργασία και σε κάποιες συγκεκριμένες θεωρίες μάθησης (πχ. Piaget). Το κύριο μέρος της διπλωματικής εργασίας αφορά την υλοποίηση ενός σεναρίου για την εκμάθηση απλών ακολουθιών ενεργειών σε παιδία προσχολικής ηλικίας, με τη βοήθεια της εφαρμογής που αναπτύχθηκε σε γραφικό περιβάλλον flash, με τον πιο ευχάριστο και δημιουργικό τρόπο. Το περιβάλλον που δημιουργήθηκε είναι κατάλληλο για τη συγκεκριμένη εφαρμογή, διότι είναι ανθρωπόμορφη και εύκολη να αλληλεπιδράσει με παιδιά μικρής ηλικίας. Το παιδί λοιπόν, θα πρέπει να φέρει σε πέρας ένα σύνολο δοκιμασιών με τη βοήθεια κάποιων συμβουλών που του δίνονται και κάποιων οδηγιών αλλά και κάποιων επιπλέον εξαρτημάτων που θα χρησιμοποιήσουμε, επιτυγχάνοντας κάθε φορά και ένα σκοπό μέχρι να ολοκληρώσει την αποστολή. Έτσι, αλληλεπιδρώντας το παιδί με το γραφικό περιβάλλον, εξοικειώνεται με τη διαδικασία επίλυσης προβλημάτων, ενώ παράλληλα γνωρίζει τα βασικά στοιχεία ενός διαδραστικού συστήματος, μαθαίνοντας να χειρίζεται εργαλεία αναγνώρισης φωνής και αφής.
Community RF sensing
(Πολυτεχνείο Κρήτης, 2012) Alimpertis Emmanouil; Αλιμπερτης Εμμανουηλ; Bletsas Aggelos; Μπλετσας Αγγελος; Garofalakis Minos; Γαροφαλακης Μινως; Lagoudakis Michael; Λαγουδακης Μιχαηλ
Compact modelling of multi-gate MOSFETs for analog design
(Πολυτεχνείο Κρήτης, 2015) Gyroukis Georgios; Γυρουκης Γεωργιος; Bucher Matthias; Bucher Matthias; Balas Costas; Μπαλας Κωστας; Kalaitzakis Kostas; Καλαϊτζακης Κωστας
Τα τελευταία χρόνια, η ραγδαία ανάπτυξη της τεχνολογίας ολοκληρωμένων κυκλωμάτων, οδήγησε στην ανάγκη για μείωση του μήκους της πύλης του τρανζίστορ MOS. Η σμίκρυνση τωνδιαστάσεων των συμβατικών τρανζίστορ τεχνολογίας CMOS αναμένεται να γίνεται ολοένα και πιο δύσκολη εξαιτίας της επίπτωσης των φαινομένων μικρού καναλιού, τα οποία διαδραματίζουν όλο και σημαντικότερο ρόλο στην απόδοση της διάταξης. Τα MOSFET πολλαπλών πυλών (multi-gate MOSFET) παρουσιάζονται να είναι οι πιο ελπιδοφόρες διατάξεις που παρέχουν την δυνατότητα επέκτασης της τεχνολογίας σε διαστάσεις νάνο-κλίμακας. Αυτό οφείλεται στο γεγονός ότι λόγο του καλύτερου ηλεκτροστατικού ελέγχου του καναλιού τα φαινόμενα μικρού μήκους καναλιού καταστέλλονται. Βασικός στόχος της παρούσας μεταπτυχιακής διατριβής είναι η ανάπτυξη συμπαγών μοντέλων στα οποία θα περιέχονται εξισώσεις για το ρεύμα απαγωγού και τις διαχωρητικότητες των τρανζίστορ πολλαπλών πυλών και πιο συγκεκριμένα ενός τρανζίστορ FinFET που υπό ορισμένες συνθήκες μπορεί να αντιμετωπιστεί ως ένα τρανζίστορ διπλής πύλης (double-gate MOSFET). Τα μοντέλα αυτά θα πρέπει να μπορούν να περιγράφουν την συμπεριφορά των διατάξεων αυτών σε όλες τις περιοχές λειτουργίας. Δηλαδή από την ασθενή έως και την ισχυρή αναστροφή, κάτω και πάνω από την τάση κατωφλίου, καθώς και από γραμμική περιοχή έως την περιοχή κορεσμού. Ο τρόπο που τα περιγράφουν θα πρέπει να είναι τέτοιος ώστε να παραμένει υπολογιστικά αποδοτικό και αξιόπιστο κατά την προσομοίωση κυκλωμάτων. Επίσης να καλύπτει όλα τα φαινόμενα που προκύπτουν από την υποκλιμάκωση των δομών αυτών και τις διαφορετικές τεχνικές που χρησιμοποιούνται για την κατασκευή. Τέλος θα πρέπει να διατηρεί την απλότητα και την ακρίβεια του. Τέλος, τα μοντέλα αυτά θα πρέπει να είναι κατάλληλα δομημένα έτσι ώστε να μπορούν να εισαχθούν στα σύγχρονα περιβάλλοντα προσομοίωσης, επιτρέποντας τον σχεδιασμό CMOS κυκλωμάτων νάνο-κλίμακας. Στα συμπαγή μοντέλα, που βασίζονται στον υπολογισμό των φορτίων που εμφανίζονται στην διάταξη (charge based compact models), ρόλο κλειδί αποτελεί η σχέση που συνδέει τα φορτία που εμφανίζονται στην διάταξη με το δυναμικό που εφαρμόζεται στους ακροδέκτες αυτής. Αποτελεί λοιπόν κομβικό σημείο η όσο το δυνατόν πληρέστερη μοντελοποίηση της. Στην παρούσα διατριβή γίνεται μελέτη της συγκεκριμένης σχέσης, κάποιων απλοποιημένων μορφών αυτής και του σφάλματος που εισάγεται στο μοντέλο από τις απλουστευμένες μορφές της. Συνεχίζοντας, στην παρούσα διατριβή μελετάται η εξάρτηση της ηλεκτρικής συμπεριφοράς των νάνο-τρανζίστορ ως προς τη φυσική σχεδίαση (layout) της διάταξης. Πέρα από τις εξαρτήσεις της διάταξης από τα μεγέθη μήκος, πλάτος (και ύψος διαύλου σε FinFET τρανζίστορ), και αριθμός δακτυλίων (fingers) υπάρχει και σημαντική εξάρτηση ως προς τις αποστάσεις από μονωτικές περιοχές, την ύπαρξη dummy (ψεύδο-τρανζίστορ) κλπ. καθώς και η ανάπτυξη κατάλληλων υποκυκλωμάτων τα οποία θα αντιπροσωπεύσουν στις στατιστικές διακυμάνσεις – τόσο σε επίπεδο τεχνολογίας (process) όσο και σε επίπεδο ταιριάσματος στοιχείο-προς-στοιχείο (device-to-device matching) – συναρτήσει των γεωμετρικών δεδομένων (layout). Τέλος, περιγράφεται και η συμπεριφορά του θορύβου των τρανζίστορ, ιδίως όσων αφορά στο θερμικό θόρυβο. Τελικό αποτέλεσμα της όλης μεταπτυχιακής αυτής διατριβής είναι η παράθεση ενός Verilog-Α κώδικα για την προσομοίωση κυκλωμάτων νάνο-τρανζίστορ πολλαπλών πυλών. Οι παράμετροι του μοντέλου προσαρμόστηκαν σε δεδομένα τύπου TCAD καθώς και σε εργαστηριακές μετρήσεις.
Correlation Study of Arterial Blood Pressure Level to the Amplitude of the Pressure Pulse Waveform
(Butterworth & Co Ltd, 1984) Vachtsevanos, G.J; Kalaitzakis K.C; Papamarkos, N; Ziakas G.; Economou K.; Gemitzis K.
Automated blood pressure measurements are usually characterized by poor operational reliability and a considerable degree of complexity in performing the measurement. This paper introduces a new technique for the indirect measurement of the systolic and diastolic blood pressure of an individual. The technique is based upon a statistically consistent relationship between the amplitude of the pulsative pressure waveform at the systolic and diastolic points, and the amplitude of pulse signals detected when the artery is fully occluded. Clinical testing and statistical analysis techniques are used to derive appropriate numerical values for these relationships. The proposed procedure thus incorporates an adaptive measurement philosophy achieving minimum observer involvement and consequently high instrument accuracy. Overall measurement errors are maintained well within proposed standards for automated sphygmomanometers.
Crowdsourcing and management of nature observational data
(Πολυτεχνείο Κρήτης, 2014) Skevakis Giannis; Σκευακης Γιαννης; Christodoulakis Stavros; Χριστοδουλακης Σταυρος; Mania Aikaterini; Μανια Αικατερινη; Deligiannakis Antonios; Δεληγιαννακης Αντωνιος
Observations of plants and animals in nature is highly valued information for the experts in the area of biodiversity. They can be used to define changes in the population of animals, plants, or track their movements throughout long periods of time. Moreover, the richer the information following the observations, the more knowledge can be extracted from them. However, the limited number of experts and the limited funding in the area, makes the observation gathering procedure almost impossible. We present the design and implementation of a framework for the management of bio- diversity observations captured by users roaming in the nature. This aims to alleviate the need for experts capturing biodiversity information, and propagates the collection of information to simple users wandering in the nature. Our framework consists of a model supporting the observations, and an infrastructure that allows the capturing, enrichment and storage of the observations using state- of-the-art technologies. Our architecture provides a scalable, highly efficient management of the collected data. The collection of the observational data is performed in real-time using mobile de- vices that most of the people have available with them, like mobile phones and tablets. Additionally, we describe the meta-model that we have defined, allowing the personalization of the metadata that follow the observations. This provides our framework with the freedom and extensibility needed so as to be implemented for various domains other than biodiversity. Finally, we describe the process of migrating the data collected by the Natural Europe project to our infrastructure.
Data classification and mapping in optical dynamic contrast-enhanced imaging of cervical neoplasia.
(Technical University of Crete, 2014) Chiou Eleni; Χιου Ελενη; Balas Costas; Μπαλας Κωστας; Zervakis Michalis; Ζερβακης Μιχαλης; Lagoudakis Michael; Λαγουδακης Μιχαηλ
Data integration approaches for supporting retrieval of medical information in the Web
(Πολυτεχνείο Κρήτης, 2015) Andrianakis Stamatios; Ανδριανακης Σταματιος; Petrakis Evripidis; Πετρακης Ευριπιδης; Lagoudakis Michael; Λαγουδακης Μιχαηλ; Samoladas Vasilis; Σαμολαδας Βασιλης
In recent years, the World Wide Web has become the basic source of scientific information. Especially for medical information, several Medical Information Systems have been developed in order to store and organize medical data and make it available to users through specialized search engines provided by them, or through general purpose search engines like Google. Vast amount of medical data available in the Web and the large number of Medical Information Systems make the search process of reliable medical information a time-consuming and sometimes difficult process. This work presents an integration method for search and retrieval of medical data and MIIDLE, an integration system for search and retrieval of medical information from heterogeneous sources. MIIDLE utilizes MeSH, the National Library of Medicine's controlled vocabulary thesaurus as a common vocabulary for the integration process. Using AMTEx method, it extracts medical terms from the retrieved data, and it expands the query used for the retrieval with MeSH terms. Combining the extracted terms with the expanded query it ranks the results with respect to their relevance using Vector Space Model. MIIDLE results are evaluated by users and its performance is compared with the performance of the sources that it accesses.
Decomposition methods for network utility maximization
(Πολυτεχνείο Κρήτης, 2015) Kostoulas Georgios; Κωστουλας Γεωργιος; Liavas Athanasios; Λιαβας Αθανασιος; Paterakis Michalis; Πατερακης Μιχαλης; Koutsakis Polychronis; Κουτσακης Πολυχρονης
Network Utility Maximization (NUM) is the problem of allocating the right amount of resources to the nodes of a network, in order to maximize an overall utility function. There are many optimization tools to solve this problem in a centralized manner. In this thesis, we discuss distributed ways to solve various formulations of NUM problems. We decompose the problems into subproblems using Primal Decomposition, by applying direct resource allocation and then adjust the resources by small steps until equilibrium, and Dual Decomposition by pricing the resource in such manner that each node achieves the optimal utility. Many alternatives can be derived from these two methods, in different NUM formulations, with the use of multilevel decompositions. These decompositions may lead to better understanding of existing networks, reverse engineering of network protocols like TCP, better management of existing networks, and ways to design and operate new networks by layering as optimization. Finally, we experiment with the message passing of these algorithms and try to minimize the data transferred by quantizing the values.
Depth perception from a single camera and multiple light sources
(Technical University of Crete, 2015) Rematska Georgia; Ρεματσκα Γεωργια; Dollas Apostolos; Δολλας Αποστολος; Papaefstathiou Ioannis; Παπαευσταθιου Ιωαννης; Zervakis Michalis; Ζερβακης Μιχαλης
3D Vision has always been a subject of research for many decades. The use of images results in the loss of the 3rd dimension. Many techniques have been developed over the years that aim in acquiring depth from images. Among the most widespread are stereo vision, fringe projection, laser scanning or combinations of them, all of which have shown high quality results but unsuitable for some classes of applications. For example, laser scanning rangefinders are not low-cost system. Hence, there is a need to develop a low cost, high speed, high resolution system for 3D vision. In this thesis a novel approach is presented to estimate depth using a single camera combined with two spectrally distinct light sources for road surface measurements. The light sources consist of two sets of LED arrays. Depth information can be extracted, by processing the different reflections in the image from the two light sources. The basic information of depth estimation lies in their blue to red ratio, which with appropriate calibration is correlated to depth. The methodology was first developed in MATLAB and then was implemented on FPGA. The system is real time and fully optimized to have the minimum hardware resources and high frequency of operation for high resolution images.
Design and development of a new electronic sphygmomanometer
(Kluwer Academic Publishers, 1985) Vachtsevanos, G.J; Kalaitzakis K.C; Papamarkos, N
The paper introduces a new technique for the indirect measurement of the systolic and diastolic blood pressure in humans. The technique is based upon a statistically consistent relationship between the amplitude of the pulsatile pressure waveform at the systolic and diastolic points and the amplitude of pulse signals detected when the artery is fully occluded. An adaptive measurement philosophy has been implemented in the design of an electronic sphygmomanometer which, in addition to a pressure transducer, contains suitable electronic instrumentation for processing and displaying the electronic signals. Verification of overall system accuracy is accomplished with direct comparison with manual auscultatory measurements. Clinical testing of a prototype indicates a satisfactory performance; measurement errors are maintained well within proposed standards for automated sphygmomanometers.
Design and implementation of a platform for the development and management of learning experiences in location-based mobile games
(Πολυτεχνείο Κρήτης, 2015) Makris Dimitrios-Ioannis; Μακρης Δημητριος-Ιωαννης; Christodoulakis Stavros; Χριστοδουλακης Σταυρος; Deligiannakis Antonios; Δεληγιαννακης Αντωνιος; Lagoudakis Michael; Λαγουδακης Μιχαηλ
Recent international surveys present that educational games can be used to promote critical thinking and enhance problem solving skills even in the early school ages. On the other hand, it is a common belief that due to the rapidly changing technology, education should be adapted in order to follow the changes and the new needs of students. To this end, any tool supporting the creation of educational learning experiences, through the use of modern devices and technologies, is considered invaluable both for educators and young learners. In this thesis we discuss the design and implementation of a platform for the development and management of learning experiences in location-based games. More specifically, we present an authoring tool (desktop application) supporting the creation and management of mobile location-based games, as well as scenario editing, user interface customization and organization of gaming activities. Furthermore, we present the player application (mobile application) that we have developed, supporting the play of games which have been created using the authoring tool. The player application is compatible with most state-of-the-art mobile devices and platforms, while both tools have been designed with flexibility and extensibility in mind. To this end, they can be used in various domains including education, museum exploration, city sightseeing, as well as in everyday gaming activities for having fun. Our applications are compatible with well known modern educational tools and repositories through the direct use of the Tin Can API. Finally, is worth mentioning that they have been evaluated for their usability by professionals and naive users.

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