Ant algorithms have been used for a variety of combinatorial optimization problems. One of these problems, where ant algorithms haven't been used, is the design of transition rules for cellular automata (CA). Which is a problem that this master's thesis is focused on. This work begins with an introduction into ant algorithms and a overview of its applications, followed by an introduction into CA. In the next part the author proposes a way how to encode rules of CA into a graph which is used in ant algorithms. The last part of this thesis contains an application of encoded graph on elitist ant system and MAX-MIN ant system. This is followed by experimental results of creating transition rules for CA problems by these algorithms.

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With the election of President Trump, climate deniers feel emboldened and moved from the fringes to the centre of global policy making. We study how an agnostic approach to policy, based on Pascal's wager and allowing for subjective prior probability beliefs about whether climate deniers are right, prices carbon. Using the DICE integrated assessment model, we find that assigning a 10% chance of climate deniers being correct lowers the global price on carbon in 2020 only marginally: from $21 to $19 per ton of carbon dioxide if policymakers apply "Nordhaus discounting" and from $91 to $84 per ton of carbon dioxide if they apply "Stern discounting". Agnostics' reflection of remaining scientific uncertainty leaves climate policy essentially unchanged. The robustness of an ambitious climate policy also follows from using the max-min or the min-max regret principle. Letting the coefficient of relative ambiguity aversion vary from zero, corresponding to expected utility analysis, to infinity, corresponding to the max-min principle, we show how policy makers deal with fundamental climate model uncertainty if they are prepared to assign prior probabilities to different views of the world being correct. Allowing for an ethical discount rate and a higher market discount rate and for a wide range of sensitivity exercises including damage uncertainty, we show that pricing carbon is the robust response under rising climate scepticism. / Series: Ecological Economic Papers

Cette thèse évalue les performances de systèmes de stockage de données sur des réseaux de pairs. Ces systèmes reposent sur trois piliers: la fragmentation des données et leur dissémination chez les pairs, la redondance des données afin de faire face aux éventuelles indisponibilités des pairs et l'existence d'un mécanisme de recouvrement des données perdues ou temporairement indisponibles. Nous modélisons deux mécanismes de recouvrement des données par des chaînes de Markov absorbantes. Plus précisément, nous évaluons la qualité du service rendu aux utilisateurs en terme de longévité et de disponibilité des données de chaque mécanisme. Le premier mécanisme est centralisé et repose sur l'utilisation d'un serveur pour la reconstruction des donnée perdus. Le second est distribué : la reconstruction des fragments perdus met en oeuvre, séquentiellement, plusieurs pairs et s'arrête dès que le niveau de redondance requis est atteint. Les principales hypothèses faites dans nos modèles sont validées soit par des simulations soit par des traces réelles recueillies dans différents environnements distribués. Pour les processus de téléchargement et de recouvrement des données nous proposons un modèle de simulation réaliste qui est capable de prédire avec précision le comportement de ces processus mais le temps de simulation est long pour de grands réseaux. Pour surmonter cette restriction nous proposons et analysons un algorithme efficace au niveau flux. L'algorithme est simple et utilise le concept de (min-max). Il permet de caractériser le temps de réponse des téléchargements en parallèle dans un système de stockage distribué.

We study energy-efficient power allocation among relays for lifetime maximization in a dual-hop relay network operated by amplify-and-forward relays with battery limitations. Power allocation algorithms are proposed for three different scenarios. First, we study the relay cooperation case where all the relays jointly support transmissions for a targeted data rate. By exploring the correlation of time-varying relay channels, we develop a prediction-based relay cooperation method for optimal power allocation strategy to improve the relay network lifetime over existing methods that do not predict the future channel state, or assume the current channel state remains static in the future. Next, we consider energy-efficient relay selection for the single source-destination case. Assuming finite transmission power levels, we propose a stochastic shortest path approach which gives the optimal relay selection decision to maximize the network lifetime. Due to the high computational complexity, a suboptimal prediction-based relay selection algorithm, directly coming from previous problem, is created. Finally, we extend our study to multiple source-destination case, where relay selection needs to be determined for each source-destination pair simultaneously. The network lifetime in the presence of multiple source-destination pairs is defined as the longest time when all source-destination pairs can maintain the target transmission rate. We design relay-to-destination mapping algorithms to prolong the network lifeii time. They all aim at maximizing the perceived network lifetime at the current time slot. The optimal max-min approach and suboptimal user-priority based approach are proposed with different levels of computational complexity. / UOIT

Title: Optimization Problems under (max, min)-Linear Constraints and Some Related Topics. Author: Mahmoud Gad Department/Institue: Department of Probability and Mathematical Statis- tics Supervisor of the doctoral thesis: 1. Prof. RNDr. Karel Zimmermann,DrSc 2. Prof. Dr. Assem Tharwat, Cairo University, Egypt Abstract: Problems on algebraic structures, in which pairs of operations such as (max, +) or (max, min) replace addition and multiplication of the classical linear algebra have appeared in the literature approximately since the sixties of the last century. The first publications on these algebraic structures ap- peared by Shimbel [37] who applied these ideas to communication networks, Cunninghame-Green [12, 13], Vorobjov [40] and Gidffer [18] applied these alge- braic structures to problems of machine-time scheduling. A systematic theory of such algebraic structures was published probable for the first time in [14]. In recently appeared book [4] the readers can find latest results concerning theory and algorithms for (max, +)-linear systems of equations and inequalities. Since operation max replacing addition in no more a group, but a semigroup oppera- tion, it is a substantial difference between solving systems with variables on one side and systems with variables occuring on both sides of the equations....

La technologie numérique rend la transmission, le stockage et la modification de documents multimedia beaucoup plus aisés qu'auparavant. Mais du fait de cette facilité, l'authentification et la gestion des droits d'auteur deviennent difficiles. Le tatouage robuste est une solution qui s'est beaucoup développée depuis une dizaine d'années. Il permet d'insérer au sein d'un document multimedia (document hôte) un message (identifiant d'auteur, signature numérique, . . .). Cette modification est peu perceptible afin de ne pas gêner l'exploitation normale du document marqué. De plus, l'algorithme d'extraction doit pouvoir retrouver le message malgré d'éventuelles modifications de l'hôte (attaques). Alors que les premières études sur ce domaine étaient empiriques, il est apparu rapidement que le tatouage était assimilable à un problème de communication. Nous faisons le choix d'utiliser une technique de transmission particulièrement adaptée aux canaux fortement bruités, appelée étalement de spectre, et nous considérons des attaques SAWGN (scaling and additive white Gaussian noise). L'interaction entre tatouage et attaques est modélisée par un jeu entre un attaquant et un défenseur. Une optimisation de type max-min donne la forme de l'attaque optimale, qui va le plus réduire la performance de la transmission, et de la stratégie qui permet de s'en protéger au mieux. L'application de ces résultats sur des signaux issus de la transformée en ondelettes d'images confirme le bien-fondé de notre approche : l'attaque obtenue est la plus efficace, et la stratégie d'insertion est bien plus performante que les techniques testées issues de l'état de l'art. Le canal de tatouage est un canal avec information adjacente : une partie du bruit (le signal hôte) est connue au moment de l'insertion de la marque. Les travaux sur ces canaux promettent des performances théoriques bien supérieures aux canaux gaussiens classiques. Dans la troisième partie de ce manuscrit, nous reprenons l'optimisation par théorie des jeux en incluant une mesure de performance prenant en compte l'information adjacente. Nous détaillons ensuite la construction d'un dictionnaire structuré adapté à ces canaux. Les expérimentations nous indiquent de forts gains de performance. Enfin, le dernier chapitre améliore le jeu : l'étude de l'influence de désynchronisations géométriques sur les performances, et la définition d'une attaque informée prenant en compte la réalisation du signal reçu.

Multicast has long been considered an attractive service for the Internet for the provision of multiparty applications. For over a decade now multicast has been a proposed IETF standard. Though there is a strong industry push towards deploying multicast, there has been little multicast deployment by commercial Internet Service Providers (ISPs) and more importantly most end-users still lack multicast capabilities. Depending on the underlying network infrastructure, the ISP has several options of implementing his multicast capabilities. With significantly faster and more sophisticated protocols being designed and prototyped, it is expected that a whole new gamut of applications that are delay sensitive will come into being. However, the incentives to resolve the conflicting interests of the ISPs and the end-users have to be provided for successful implementation of these protocols. Thus we arrive at the following economic questions: What is the strategy that will enable the ISP recover his costs ? How can the end-user be made aware of the cost of his actions ? Naturally, the strategies of the ISP and the end-user depend on each other and form an economic game. The research problems addressed in this thesis are: A pricing model that is independent of the underlying transmission protocols is prefered. We have proposed such a pricing scheme for multicast independent of the underlying protocols, by introducing the concept of pricing points* These pricing points provide a range of prices that the users can expect during a particular time period and tune their usage accordingly. Our pricing scheme makes both the sender and receiver accountable. Our scheme also provides for catering to heterogeneous users and gives incentive for differential pricing. We explore a number of formulations of resource allocation problems arising in communication networks as optimization models. Optimization-based methods were only employed for unicast congestion control. We have extended this method for single rate multicast. We have also devised an optimization-based approach for multicast congestion control that finds an allocation rate to maximize the social welfare. Finally we also show that the session-splitting problem can also be cast as an optimization problem. The commonly used "max-min" fairness criteria suffers from serious limitations like discriminating sessions that traverse large number of links and poor network utilization. We provide an allocation scheme that reduces discrimination towards multicast sessions that traverse many links and also improves network utilization.

This thesis deals with DBA algorithms used in XG-PON networks. It describes reference appearance of the DBA algorithm, as well as, three specific DBA algorithms discussed in professional articles. Particularly speaking about GIANT, HYRA and modified Max-Min Fair DBA. The thesis provides description of frames utilized by DBA algorithms in XG-PON networks, specifically XGEM frame and XGTC frames. The thesis also presents a simulation tester of DBA algorithms tested on a virtual XG-PON network. Finally, it contains the results of testing these DBA algorithms with a description.

This work deals with the issue of swarm intelligence as a subdiscipline of artificial intelligence. It describes biological background of the dilemma briefly and presents the principles of searching paths in ant colonies as well. There is also adduced combinatorial optimization and two selected tasks are defined in detail: Travelling Salesman Problem and Quadratic Assignment Problem. The main part of this work consists of description of swarm intelligence methods for solving mentioned problems and evaluation of experiments that were made on these methods. There were tested Ant System, Ant Colony System, Hybrid Ant System and Max-Min Ant System algorithm. Within the work there were also designed and tested my own method Genetic Ant System which enriches the basic Ant System i.a. with development of unit parameters based on genetical principles. The results of described methods were compared together with the ones of classical artificial intelligence within the frame of both solved problems.