Network resiliency pertains to the vulnerability of telecommunication networks in the case of failures and malicious attacks. With the increasing capacity catering of network for the booming multi-services in Next Generation Networks (NGNs), reducing recovery time and improving capacity efficiency while providing high quality and resiliency of services has become increasingly important for the future network development. Providing network resiliency means to rapidly and accurately reroute the traffic via diversely routed spare capacity in the network when a failure takes down links or nodes in the working path. Planning and optimization for NGNs require an efficient algorithm for spare capacity allocation (SCA) that assures restorability with a minimum of total capacity. This dissertation aims to understand and advance the state of knowledge on spare capacity allocation in network resiliency for telecommunication core networks. Optimal network resiliency design for restorability requires considering: network topology, working and protection paths routing and spare capacity allocation. Restorable networks should be highly efficient in terms of total capacity required for restorability and be able to support any target level of restorability. The SCA strategy is to decide how much spare capacity should be reserved on links and to pre-plan protection paths to protect traffic from a set of failures. This optimal capacity allocation problem for survivable routing is known as NP-complete. To expose the problem structure, we propose a model of the SCA problem using a matrix-based framework, named Distributed Resilience Matrix (DRM) to identify the dependencies between the working and protection capacities associated with each pair of links and also to capture the local capacity usage information in a distributed control environment. In addition, we introduce a novel ant-based heuristic algorithm, called Friend-or-Foe Resilient (FoF-R) ant-based routing algorithm to find the optimal protection cycle (i.e., two node-disjoint paths between a source-destination node pair) and explore the sharing ability among protection paths using a capacity headroom-dependent attraction and repulsion function. Simulation results based on the OMNeT++ and AMPL/CPLEX tools show that the FoF-R scheme with the DRM structure is a promising approach to solving the SCA problem for survivable routing and it gives a good trade off between solution optimality and computation speed. Furthermore, for the SCA studies of survivable networks, it is also important to be able to differentiate between network topologies by means of a robust numerical measure that indicates the level of immunity of these topologies to failures of their nodes and links. Ideally, such a measure should be sensitive to the existence of nodes or links, which are more important than others, for example, if their failure causes the network’s disintegration. Another contribution in this dissertation is to introduce an algebraic connectivity metric, adopted from the spectral graph theory, namely the 2nd smallest eigenvalue of the Laplacian matrix of the network topology, instead of the average nodal degree, to characterize network robustness in studies of the SCA problem. Extensive simulation studies confirm that this metric is a more informative parameter than the average nodal degree for characterizing network topologies in network resiliency studies.

This thesis presents an application of the Ant Colony algorithm for optimizing filter placement and sizing on a radial distribution system to reduce power losses and keep the effective harmonic voltage values and the total harmonic distortion (THD) within prescribed limits. First, a harmonic load flow (HLF) algorithm is performed to demonstrate the effect of harmonic sources on total power loss. Then the Ant Colony algorithm is used in conjunction with HLF to place a selection of filter sizes available at each possible location so that both power loss and THD are minimized. As a result the optimal adjustment of location and size of the filter are determined. Results of computational experiments on standard test systems are presented to demonstrate improvement and effectiveness of using the filters at the optimal location. The methodology used can be easily extended to different distribution network configurations. / Master Thesis

Sensor failures or oversupply in wireless sensor networks (WSNs), especially initial random deployment, create both spare sensors (whose area is fully covered by other sensors) and sensing holes. We envision a team of robots to relocate sensors and improve their area coverage. Existing algorithms, including centralized ones and the only localized G-R3S2, move only spare sensors and have limited improvement because non-spare sensors, with area coverage mostly overlapped by neighbour sensors, are not moved, and additional sensors are deployed to fill existing holes. We propose a localized algorithm, called Localized Ant-based Sensor Relocation Algorithm with Greedy Walk (LASR-G), where each robot may carry at most one sensor and makes decision that depends only on locally detected information. In LASR-G, each robot calculates corresponding pickup or dropping probability, and relocates sensor with currently low coverage contribution to another location where sensing hole would be significantly reduced. The basic algorithm optimizes only area coverage, while modified algorithm includes also the cost of robot movement. We compare LASR-G with G-R3S2, and examine both single robot and multi robots scenarios. The simulation results show the advantages of LASR-G over G-R3S2.

Vehicular Ad hoc Networks (VANET) exhibit highly dynamic behavior with high mobility and random network topologies. The performance of Transmission Control Protocols in such wireless ad hoc networks is plagued by a number of problems: frequent link failures, scalability, multi-hop data transmission and data loss. To address these VANET routing issues, I have used the ideas from swarm intelligence. The Ant Colony Optimization (ACO), which is a branch of swarm intelligence, is the main source of my inspiration. I have designed an ant-based routing algorithm which addresses routing issues prevalent in VANETs: adaptivity, robustness and scalability. One attractive feature of ACO is that they provide multiple routes from source to destination, resulting in more robust network. In this work, together with ACO, I have used the ideas from zone routing protocols to develop my algorithm: Mobility Aware Zone based Ant Colony Optimization Routing for VANET that exhibits locality and scalability.

This dissertation builds upon the existing body of criminological and socio-legal literature on Internet governance by looking at how this technology and its use are regulated in Canada. Rather than focusing on the regulation of specific web-based activities (e.g., illegal downloading, child luring, etc.) or the control of certain types of online content (e.g., hate speech, pornography, etc.), the dissertation considers the ways that regulatory bodies have responded to the emergence of this new medium. Three specific agencies involved in the governing of the Internet are studied in detail: The Canadian Radio-television and Telecommunications Commission (CRTC), the Media Awareness Network (MNet) and the courts. Using a variety of theoretical and conceptual tools taken from both governmentality studies and Actor-Network Theory (ANT), the dissertation empirically documents how these agencies imagine the Internet and make it governable. Instead of searching for global accounts that look to either Society or Technology as a source of explanation for why the technology is governed in a particular fashion, this project examines how certain knowledges about the Internet and its regulation get produced in the first place. Attention is paid here to how these agencies initially problematize the Internet, the kinds of regulatory strategies and practices that have emerged and the general impact this has had for our understanding of the Internet and the way in which it should be governed. In keeping with the constructivist tradition in the field of Science and Technology Studies (S&TS), the dissertation approaches the regulation of the Internet as a site where the very nature of this technology – in terms of what it does, how it can be used and whether or not it can or should be regulated – gets invented and reinvented. However, rather than bracketing the building of the Internet from its governance, these processes are seen as mutually constitutive whereby the technology must be made governable in order to be governed. Consequently, given the many different and often competing visions about the Internet, the version that gets accepted (at least, momentarily) is shown to be crucial for how the technology is eventually received.

This dissertation builds upon the existing body of criminological and socio-legal literature on Internet governance by looking at how this technology and its use are regulated in Canada. Rather than focusing on the regulation of specific web-based activities (e.g., illegal downloading, child luring, etc.) or the control of certain types of online content (e.g., hate speech, pornography, etc.), the dissertation considers the ways that regulatory bodies have responded to the emergence of this new medium. Three specific agencies involved in the governing of the Internet are studied in detail: The Canadian Radio-television and Telecommunications Commission (CRTC), the Media Awareness Network (MNet) and the courts. Using a variety of theoretical and conceptual tools taken from both governmentality studies and Actor-Network Theory (ANT), the dissertation empirically documents how these agencies imagine the Internet and make it governable. Instead of searching for global accounts that look to either Society or Technology as a source of explanation for why the technology is governed in a particular fashion, this project examines how certain knowledges about the Internet and its regulation get produced in the first place. Attention is paid here to how these agencies initially problematize the Internet, the kinds of regulatory strategies and practices that have emerged and the general impact this has had for our understanding of the Internet and the way in which it should be governed. In keeping with the constructivist tradition in the field of Science and Technology Studies (S&TS), the dissertation approaches the regulation of the Internet as a site where the very nature of this technology – in terms of what it does, how it can be used and whether or not it can or should be regulated – gets invented and reinvented. However, rather than bracketing the building of the Internet from its governance, these processes are seen as mutually constitutive whereby the technology must be made governable in order to be governed. Consequently, given the many different and often competing visions about the Internet, the version that gets accepted (at least, momentarily) is shown to be crucial for how the technology is eventually received.

Les inflorescències on és present la formiga argentina reben menys visitants, a les zones envaïdes, a més, desapareixen la majoria d'espècies de formigues autòctones, algunes de les quals podrien ser pol·linitzadores d'algunes espècies vegetals. Aquest efecte repel·lent i la desaparició de formigues autòctones es tradueix en una menor producció de fruits en plantes com Euphorbia characias o Euphorbia biumbellata / Argentine ant effects on pollination of several mediterranean species

Combinatorial optimisation problems (COPs) pervade human society: scheduling, design, layout, distribution, timetabling, resource allocation and project management all feature problems where the solution is some combination of elements, the overall value of which needs to be either maximised or minimised (i.e., optimised), typically subject to a number of constraints. Thus, techniques to efficiently solve such problems are an important area of research. A popular group of optimisation algorithms are the metaheuristics, approaches that specify how to search the space of solutions in a problem independent way so that high quality solutions are likely to result in a reasonable amount of computational time. Although metaheuristic algorithms are specified in a problem independent manner, they must be tailored to suit each particular problem to which they are applied. This thesis investigates a number of aspects of the application of the relatively new Ant Colony Optimisation (ACO) metaheuristic to different COPs.The standard ACO metaheuristic is a constructive algorithm loosely based on the foraging behaviour of ant colonies, which are able to find the shortest path to a food source by indirect communication through pheromones. ACO’s artificial pheromone represents a model of the solution components that its artificial ants use to construct solutions. Developing an appropriate pheromone representation is a key aspect of the application of ACO to a problem. An examination of existing ACO applications and the constructive approach more generally reveals how the metaheuristic can be applied more systematically across a range of COPs. The two main issues addressed in this thesis are biases inherent in the constructive process and the systematic selection of pheromone representations.The systematisation of ACO should lead to more consistently high performance of the algorithm across different problems. Additionally, it supports the creation of a generalised ACO system, capable of adapting itself to suit many different combinatorial problems without the need for manual intervention.

Thesis (M.S.) -- Mississippi State University. Department of Entomology and Plant Pathology. / Title from title screen. Includes bibliographical references.

Στην παρούσα εργασία γίνεται μια προσπάθεια συνολικής παρουσίασης των τεχνικών χρονοπρογραμματισμού έργου ακολουθώντας την πορεία εξέλιξής τους. Στο τρίτο κεφάλαιο απαντάμε στα βασικά ερωτήματα που αφορούν το τι περιλαμβάνει η έννοια του όρου έργο και διαχείριση έργου. Είναι πολύ σημαντικό πριν να προχωρήσουμε σε τεχνικές χρονοπρογραμματισμού ενός έργου να μπορούμε να αποκωδικοποιήσουμε τις ανάγκες του αλλά και τον τρόπο δόμησής του ώστε να υπολογίσουμε σωστά τις ανάγκες και τα κόστη σε χρόνο αλλά και σε πόρους, ώστε να φθάσουμε στην επίτευξη του τελικού σκοπού μέσα στο χρονικό ορίζοντα που έχουμε θέσει και χωρίς να έχουμε αποκλίσεις από τις προϋπολογισθείσες δαπάνες πόρων. Στη συνέχεια αναλύονται οι κλασικές τεχνικές χρονοπρογραμματισμού μέσα από παραδείγματα εφαρμογών. Στο τέταρτο κεφάλαιο γίνεται μια παρουσίαση των βασικότερων μεθόδων επίλυσης προβλημάτων συνδυαστικής βελτιστοποίησης και παρουσιάζονται οι προσεγγίσεις αντιμετώπισης μέσω τριών κατηγοριών αλγορίθμων που έχουν αναπτυχθεί τα τελευταία χρόνια. Αυτοί είναι: οι ακριβείς μέθοδοι μαθηματικού προγραμματισμού, οι ευρετικοί αλγόριθμοι και οι μεταευρετικοί αλγόριθμοι. Στη συνέχεια δίνεται έμφαση στην παρουσίαση των κυριότερων εκπροσώπων των ακριβών μεθόδων. Αναλύουμε τις ευρετικές και μεταευρετικές μεθόδους όπως αυτές έχουν παρουσιαστεί τα τελευταία χρόνια από τους ερευνητές. Οι ευρετικές μέθοδοι αποτελούν τη πηγή έμπνευσης θα λέγαμε για τη δημιουργία των μεταευρετικών αλγορίθμων οι οποίοι υπόσχονται ακόμα καλύτερη αντιμετώπιση του προβλήματος καθώς δίνουν μια απάντηση σε προβλήματα που θεωρούνταν αδύνατο να λυθούν αποτελεσματικά και να επιστρέψουν βέλτιστες λύσεις με τους ευρετικούς αλγόριθμους. Στο πέμπτο κεφάλαιο αναλύεται η φιλοσοφία, η εξέλιξη και ο τρόπος λειτουργίας των αλγόριθμων του μοντέλου της κοινωνίας των μυρμηγκιών και γίνεται παρουσίαση των διάφορων εκδόσεων τους των τελευταίων 3 δεκαετιών που αυτοί έχουν κάνει αισθητή της παρουσία τους στην έρευνα. Γίνεται επίσης παρουσίαση τους σε μορφή ψευδοκώδικα και διαγραμμάτων ροής. Κύριο μέρος του κεφαλαίου λαμβάνει η αντιμετώπιση του Προβλήματος του Περιοδεύοντας Πωλητή (Traveling Salesman Problem- TSP) που είναι το κυριότερο πρόβλημα χρονοπρογραμματισμού και πάνω στο οποίο στηρίζεται η εύρεση λύσεων και σε άλλα υπολογιστικά προβλήματα όπως αυτό της δρομολόγησης οχημάτων, χρονοπρογραμματισμού παραγωγής κα. Στο έκτο κεφάλαιο γίνεται παρουσίαση του τρόπου αντιμετώπισης του προβλήματος της εύρεσης της κρίσιμης διαδρομής σε ένα έργο και παρουσιάζεται ο αλγόριθμος που ακολουθείται. Παράλληλα, παρουσιάζεται μια μελέτη συμπεριφοράς του αλγορίθμου σε μεταβολές των μεταβλητών του. Στο έβδομο κεφάλαιο βλέπουμε κάποια γενικά συμπεράσματα και μελλοντικές κατευθύνσεις ενώ στο Παράρτημα Ι γίνεται παρουσίαση της θεωρίας των γράφων για να γίνει καλύτερα κατανοητή η χρήση τους και ο σπουδαίος ρόλος τους στην ανάπτυξη των αλγορίθμων χρονοπρογραμματισμού, ενώ στο Παράρτημα ΙΙ παρουσιάζεται αναλυτικά το πρόβλημα του πλανόδιου πωλητή. / -