Learning to detect video events from zero or very few video examples

In this work we deal with the problem of high-level event detection in video. Specifically, we study the challenging problems of i) learning to detect video events from solely a textual description of the event, without using any positive video examples, and ii) additionally exploiting very few positive training samples together with a small number of ``related'' videos. For learning only from an event's textual description, we first identify a general learning framework and then study the impact of different design choices for various stages of this framework. For additionally learning from example videos, when true positive training samples are scarce, we employ an extension of the Support Vector Machine that allows us to exploit ``related'' event videos by automatically introducing different weights for subsets of the videos in the overall training set. Experimental evaluations performed on the large-scale TRECVID MED 2014 video dataset provide insight on the effectiveness of the proposed methods.Comment: Image and Vision Computing Journal, Elsevier, 2015, accepted for publicatio

Dis-placing the world: Nomadic politics in Mona Hatoum’s living cartographies of passages

Στο χώρο της σύγχρονης τέχνης και συγκεκριμένα στο έργο της διασπορικής καλλιτέχνιδας Mona Hatoum στρέφεται το παρόν κείμενο. Κινούμενο σε πολλαπλές διαδρομές μετατοπίσεων και εκτοπίσεων, μεταξύ Παλαιστίνης, Λιβάνου και Βρετανίας, το έργο της ενσωματώνει «χαρτογραφίες περασμάτων», που εκ-τοπίζουν τον κόσμο και τις καθιερωμένες απεικονίσεις του. Καθώς επανεγγράφει σύγχρονες ιστορίες διαφυγής και περιχαράκωσης, αποσταθεροποιεί κυρίαρχες εννοιολογήσεις του «οίκου» και του «κόσμου». Πρόκειται για ένα έργο που, μέσα από τις συνυφασμένες χωρογραφίες και σωματογραφίες πουυλοποιεί, ανοίγει δρόμους εναλλακτικής κατανόησης των ιεραρχικών προκείμενων της οικουμενικότητας αλλά και του δυνάμει ανατρεπτικού δυναμικού της «ξενότητας» και του «ανήκειν».The present essay draws from contemporary art and particularly from the art of the diasporic artist Mona Hatoum. Hers is an art about a corporeal subjectivity attuned to a living cartography of passages between Palestine, Lebanon, and England. I explore her art work with intersecting cartographies and corporealities, by focusing on her artistic gestures of displacing established notions of “home” and the “world”, in all their gendered implications. I try to unravel the ways in which Mona Hatoum keeps us on the alert for the hierarchies of false and abstract universalism, while, at the same time, keeps open the promise (and the question) for the potential subversiveness of “foreignness” and “belonging”

Regulation of MYC transcription in 3D : Implications for tumor development

This thesis uncovers how chromatin organization conspires with nuclear architecture and environmental stimuli in order to regulate gene expression in disease and particular, in cancer. In Paper I, we have unraveled a mechanism of oncogenesis, previously unknown in humans, and widely known as gene gating. Specifically, we have shown that in human colon cancer cells (HCT116) the oncogenic super-enhancer (OSE) of MYC increases its expression levels post-transcriptionally, by tethering MYC to the nuclear pore complex (NPC). This process facilitates the export of MYC transcripts to the cytoplasm and enables them to escape the rapid decay taking place in the nucleus. This phenomenon does not seem to be present in the healthy counterparts of these cells, human colon epithelial cells (HCECs), indicating that this is a unique feature of cancer. Moreover, our findings show that this mechanism is mediated by AHCTF1 (also known as ELYS): a mobile nucleoporin, part of the NPC, that binds on chromatin. Finally, it is also regulated by the canonical WNT signaling pathway and the complex formation between TCF4 and β-catenin, as shown by the use of the inhibitor BC21. In Paper II, we have further explored the molecular factors involved in the gating of MYC, as well as provided the first genetic evidence of this mechanism in humans. More precisely, by using CRISPR-Cas9 genetic engineering we generated two different clones with a mutated CTCF binding site (CTCFBS) within the OSE and showed that their inability to efficiently bind CTCF is associated with reduced MYC mRNA export. In addition, this process confers to the wild type cells a growth advantage over the mutant cells and requires the canonical WNT signaling pathway for the recruitment of the OSE from intra-nucleoplasmic positions. Our findings furthermore indicate that once the OSE has reached a peripheral position (<0.7um), the CTCFBS-mediated CCAT1 eRNA activation takes place and promotes the recruitment of AHCTF1 to the CTCFBS. That will ultimately lead to the efficient tethering of MYC to the nuclear pores and its subsequent gating, whilst pointing out the existence of a novel WNT/β-catenin-AHCTF1-CTCF-eRNA circuit in the regulation of pathogenic MYC expression. In summary, the findings covered by the present thesis provide new insights in the regulation of oncogenic MYC expression by the 3D nuclear architecture and widen our understanding on the processes underlying tumor development. Such knowledge can improve the diagnosis, as well as potentially contribute to the identification of new therapeutic targets in cancer therapy

Electromechanics of an Ocean Current Turbine

The development of a numeric simulation for predicting the performance of an Ocean Current Energy Conversion System is presented in this thesis along with a control system development using a PID controller for the achievement of specified rotational velocity set-points. In the beginning, this numeric model is implemented in MATLAB/Simulink® and it is used to predict the performance of a three phase squirrel single-cage type induction motor/generator in two different cases. The first case is a small 3 meter rotor diameter, 20 kW ocean current turbine with fixed pitch blades, and the second case a 20 meter, 720 kW ocean current turbine with variable pitch blades. Furthermore, the second case is also used for the development of a Voltage Source Variable Frequency Drive for the induction motor/generator. Comparison among the Variable Frequency Drive and a simplified model is applied. Finally, the simulation is also used to estimate the average electric power generation from the 720 kW Ocean Current Energy Conversion System which consists of an induction generator and an ocean current turbine connected with a shaft which modeled as a mechanical vibration system

Electromechanics of an Ocean Current Turbine

The development of a numeric simulation for predicting the performance of an Ocean Current Energy Conversion System is presented in this thesis along with a control system development using a PID controller for the achievement of specified rotational velocity set-points. In the beginning, this numeric model is implemented in MATLAB/Simulink® and it is used to predict the performance of a three phase squirrel single-cage type induction motor/generator in two different cases. The first case is a small 3 meter rotor diameter, 20 kW ocean current turbine with fixed pitch blades, and the second case a 20 meter, 720 kW ocean current turbine with variable pitch blades. Furthermore, the second case is also used for the development of a Voltage Source Variable Frequency Drive for the induction motor/generator. Comparison among the Variable Frequency Drive and a simplified model is applied. Finally, the simulation is also used to estimate the average electric power generation from the 720 kW Ocean Current Energy Conversion System which consists of an induction generator and an ocean current turbine connected with a shaft which modeled as a mechanical vibration system

Impact of distributed generation mix on the effectiveness of islanded operation detection

Distributed generation can be understood as a process where large scale power generation is gradually replaced by smaller power generation facilities with reduced power yield, and mostly connected at the system distribution level. One of the most important requirements for interconnecting distributed generation to healthy power networks is the Loss of Mains (or Islanding) detection. During a Loss of Mains (LOM) event a part of the grid (including distributed generation) losses physical connection with rest of the grid. A condition like this should be detected and actions to disconnect distributed generation should be initiated, in order to protect life and property. A very common passive method used to detect an islanding event, is the Rate of Change of Frequency (ROCOF). Since distribution networks nowadays are accommodating a great amount converter-interfaced generation, there is a risk that such methods may fail to successfully operate or operate spuriously, putting system stability at risk. Most of the existing LOM protection performance studies, consider only a single generator within the islanded part of the network. While historically such approach was reasonable, rapidly increasing numbers of DG connections lead to high probability of islanding with more than one generator in the mix. Therefore, this paper, considers various mixes of generation to investigate how this impacts LOM detection performance. In particular studies are undertaken with a few identified most likely combinations of distributed generators

Performance of loss-of-mains detection in multi-generator power islands

This paper presents an investigation of the impact of multi-generator power islands on the performance of the most-commonly used anti-islanding protection method, Rate of Change of Frequency (ROCOF). In particular, various generating technology mixes including Photovoltaic panels (PV), Doubly Fed Induction Generators (DFIGs) and Synchronous Generators (SG) are considered. The Non-Detection Zone (NDZ) for a range of ROCOF setting options is assessed systematically and expressed as a percentage of generator MVA rating. It was discovered that ROCOF protection becomes very ineffective when protection time delay is applied. In the majority of islanding situations the generator is disconnected by frequency-based G59 protection

Protection of microgrid with high amounts of renewables : challenges and solutions

Microgrid is a small-scale network including generators, loads and storage system, which provides a friendly way for the penetration of renewables and releases the burden of transmission system arising from the increased energy demand. Moreover, since microgrid can operate in islanded mode, it can provide backup power to local consumers when the main grid is disconnected. However, the utilization of microgrid causes serious problems in the area of power system protection. The main issues comprise varied fault levels in different operating modes and fault detection in islanded microgrid particularly when the microgrid is dominated by inverter based DGs (IIDGs). In addition, to avoid non-necessary power losses raised from multi-stage power conversion of DC loads and generators, DC microgrid becomes another attractive choice, which further increases the difficult on designing protection system for the futuristic microgrid. In this paper, a comprehensive review of the existing issues and protection methods for AC and DC microgrids is presented. Furthermore, to facilitate better understanding to readers, the benefits and limitations of each method are discussed in depth. Potential protection tools for future microgrid are suggested at the end of this paper