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Palisse, Aurélien. "Analyse et détection de logiciels de rançon." Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1S003/document.
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La thèse s'intéresse aux logiciels de rançon, présente une plateforme d'analyse automatique et propose des contre-mesures. Nos contre-mesures sont conçues pour être temps réel et déployées sur une machine, c'est-à-dire ''End-Hosts''. En 2013 les logiciels de rançon font de nouveau parler d'eux, pour finalement devenir une des menaces les plus sérieuses à partir de 2015. Un état de l'art détaillé des contre-mesures existantes est fourni. On peut ainsi situer les contributions de cette thèse par rapport à la littérature. Nous présentons également une plateforme d'analyse automatique de logiciels malveillants composée de machines nues. L'objectif est de ne pas altérer le comportement des échantillons analysés. Une première contre-mesure basée sur l'utilisation d'une librairie cryptographique par les logiciels de rançon est proposée. Celle-ci peut être facilement contournée. Nous proposons donc une seconde contre-mesure générique et agnostique. Cette fois, des indicateurs de compromission sont utilisés pour analyser le comportement des processus sur le système de fichiers. Nous détaillons comment de manière empirique nous avons paramétré cette contre-mesure pour la rendre~: utilisable et efficace. Un des challenges de cette thèse étant de faire concilier performance, taux de détection et un faible taux de faux positifs. Enfin, les résultats d'une expérience utilisateur sont présentés. Cette expérience analyse le comportement des utilisateurs face à une menace. En dernière partie, nous proposons des améliorations à nos contributions mais aussi des pistes à explorerThis phD thesis takes a look at ransomware, presents an autonomous malware analysis platform and proposes countermeasures against these types of attacks. Our countermeasures are real-time and are deployed on a machine (i.e., end-hosts). In 2013, the ransomware become a hot subject of discussion again, before becoming one of the biggest cyberthreats beginning of 2015. A detailed state of the art for existing countermeasures is included in this thesis. This state of the art will help evaluate the contribution of this thesis in regards to the existing current publications. We will also present an autonomous malware analysis platform composed of bare-metal machines. Our aim is to avoid altering the behaviour of analysed samples. A first countermeasure based on the use of a cryptographic library is proposed, however it can easily be bypassed. It is why we propose a second generic and agnostic countermeasure. This time, compromission indicators are used to analyse the behaviour of process on the file system. We explain how we configured this countermeasure in an empiric way to make it useable and effective. One of the challenge of this thesis is to collate performance, detection rate and a small amount of false positive. To finish, results from a user experience are presented. This experience analyses the user's behaviour when faced with a threat. In the final part, I propose ways to enhance our contributions but also other avenues that could be explored
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Dallaire, Marc. "Les jeunes de la rue, la rançon d'une fausse liberté." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0017/MQ56397.pdf.
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Veilleux, Denis. "La motorisation, ou, "La rançon du progrès" : tramways, véhicules-moteurs et circulation (Montréal, 1900-1930)." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=35641.
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The subject of this thesis is a technology, the motor vehicle, that greatly affected our society. Between 1900 and 1930, motorization progressed rapidly in the Montreal area as the motor vehicle became a dominant mode of urban transportation. But to reach such a status, the new technology needed more than an increasing number of people adopting it. Because the street was already occupied by different users, automobile drivers had to impose the motor car on it. Above all, it was with tramway promoters that they had to "negociate".This negotiation related to both the space available in the street and the movement of vehicles. Concerning space, the omnipresence of tramways and their installations along with the parking of motor vehicles, particularly in the downtown area of Montreal, led to suggestions of wide boulevards and subway systems as possible solutions. The fact that tramways had priority in traffic and could not be passed by motor vehicles constituted major obstacles for motorists anxious to benefit from the motor car. By the end of the 1920s, conflicts were so intense that the notion of progress was used to promote both the motor vehicle and the tramway.
These conflicts over the sharing of streets had other implications. First, different sections of Montreal's elite favoured one technology over the other. On the one hand, motorists were well organized. At the same time, tramway concerns were determined to protect their monopoly. This animosity within the elite was intensified by antimonopoly feelings and by dissatisfaction with tramway service. Finally, traffic problems multiplied with motorization: deaths, accidents, law suits and downtown congestion. Traffic became an important preoccupation leading to an increase in police forces and the establishment of numerous organizations dedicated to traffic management.
The popular classes of Montreal were not excluded from these conflicts among the elites. Generally speaking, the entire population was forced to take sides with one group of promoters or the other. Motorization then appears as a factor of division within social classes as well as a phenomenon transcending the barriers between them.
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Mammadov, Khalid. "La Cour européenne des droits de l'homme, de réforme en réforme : la rançon d'un succès ?" Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAA031.
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La Cour Européenne des droits de l’homme, depuis les années 1990, connait une extension de ses compétences ratione personae et ratione loci sans précèdent. Faire face à ce phénomène exceptionnel requiert des instruments nouveaux. L’objet de cette étude réside dans l’examen des techniques adaptées par la Cour afin de maintenir le niveau de protection des droits de l’homme garantis par la Convention. Par ailleurs les organes et les Etats membres du Conseil de l’Europe participèrent grandement à l’effort de conservation du niveau d’excellence de protection des droits de l’homme en Europe. Ce sont ces aspects précis qui sont passés en revue et apprécié sous l’angle de leurs apports et parfois, inconvénients. Sujet d’étude apporté dans un espace-temps précis, il demanderait dans un avenir d’être complété et apprécié sous cet angleThe European Court of Human Rights, since the 1990s, recognizes an unprecedented extension of its competence ratione personae and ratione loci. In order to face this exceptional phenomenon new instruments are required. The purpose of this study is the examination of new techniques adapted by the Court to maintain the level of protection of human rights guaranteed by the Convention. Other organs and Member States of the Council of Europe participated actively to the efforts in order to conserve the excellent level for the protection of human rights in Europe. These are specific areas having been reviewed and valued in terms of their contribution and sometimes their disadvantages. Prepared in a particular space-time, this study would ask in the future to be completed and assessed from this angle
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Lollia, Fabrice. "Aide à la décision en situation de crise. Les nouvelles technologies pour la prévention sécuritaire des entreprises : limites et opportunités." Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC0031.
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Le contexte sécuritaire actuel montre aujourd’hui des difficultés croissantes pour l’entreprise en termes de protection de ses collaborateurs (expatriés, voyageurs d’affaires). Les risques connus antérieurement, tels que le kidnapping contre rançon, perdurent, se développent et connaissent de nouvelles formes, tant humaines que matérielles et immatérielles. En effet, le kidnapping, qu’il soit humain, matériel ou immatériel, connaît de nombreuses formes et s’adapte selon l’objectif des auteurs, la culture du pays et son niveau sociopolitique. Face à ce fléau, l’entreprise est très ciblée tant par les auteurs que par les recours juridiques exercés contre elle en termes de responsabilité. Il s’agit donc d’un risque omniprésent, et seule une attitude proactive pourrait y remédier ou au moins le diminuer. Après avoir étudié précisément le kidnapping contre rançon et ses apports théoriques divers, nous l’avons analysé en utilisant en partie la grille de lecture de la sémiotique situationnelle d’Alex Mucchielli, les recherches de Rachel Briggs en sciences politiques, et les apports de la psychologie sociale avec notamment le syndrome de Stockholm. Tout au long de cette thèse en recherche-action, nous avons utilisé une méthode d’enquête exploratoire avec un positionnement interprétatiste et situationniste. Méthode qui, selon nous, est la plus adaptée pour l’étude du domaine de la sécurité. Nous avons ensuite créé une solution numérique nommée « application de prévention sécuritaire pour expatriés et voyageurs d’affaires » (APSEV) afin de donner un sens concret et opérationnel à nos travaux. Cette solution a été testée et validée en mission de protection au sein de l’ambassade de France en Afghanistan. Mais, au-delà de sa création, nous avons exploré son impact dans l’ambassade en termes d’interactions humaines. L’outil a été accepté par certains se sentant protégés et refusé par d’autres se sentant surveillés. Cette nouvelle technologie de sécurité dérange par son activité de géolocalisation dont le sens diverge selon les individus. Le problème sécuritaire du kidnapping contre rançon ne peut donc être résolu que par la création d’une solution numérique de géolocalisation adaptée et prenant en compte les effets sur les interactions humaines, qui permettront d’en faire un usage adéquatThe current security context shows difficulties for the company in the protection of these employees (expatriates, business travelers). Previously known risks such as kidnapping against perdition are developing and experiencing new human forms that material and immaterial. Indeed, the kidnapping that is human, material or immaterial knows many forms of appearance and adapts according to The esperancy is followed against it in terms of responsibility. It is therefore only an omnipresent risk of which only one proactive attitude could be to reduce the risk. After studying, the kidnapping against deployment and its theoretical contributions. We were analyzed using part of the reading grid of the situational semiotics of Alex Mucchielli. Throughout this page in search action used method on main-exploration exploration with a situation Method that is most suitable for studying the field of security. We then created a digital solution Application of prevention for expatriates and corporate travelers (APSEV) to give a concrete and operational meaning to our work. This solution has been tested and validated as a protection mission at the Embassy of France in Afghanistan. But beyond its creation we explored its impact in the embassy in terms of human interaction. Accepted by some who feel protected and denied by others who feel guarded. This new security technology is disturbing because of its geolocation activity, whose meaning varies from one individual to another. The security problem of kidnapping against ransom can only be solved by the creation of a suitable geolocalisation digital solution without taking into account the effects on human interactions that will make it suitable for use
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Bosco, Michele. "Ragion di Stato e salvezza dell’anima. Il riscatto dei cristiani captivi in Maghreb attraverso le redenzioni mercedarie (1575 - 1725)." Thesis, Paris, EHESS, 2017. http://www.theses.fr/2017EHES0037.
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Dans le but d’éclairer les dynamiques économiques et les mécanismes institutionnels qui régulaient le rachat des chrétiens captifs au Maghreb aux siècles centraux de l’époque moderne, l’auteur se propose de reconstruire l’activité rédemptrice de l’un des indiscutables protagonistes de ce commerce: l’Ordre de Notre Dame de la Merci. Pour en illustrer les spécificités, l’auteur présente d’abord de façon général le phénomène des rachats des captifs entre les XVIe et le XVIIIe siècles en Méditerranée, dans le contexte de la guerre de course qui se déroulait entre ses rives. Par la suite, il retrace de façon synthétique l’histoire de l’Ordre de la Merci, de son expansion et de son progressif développement dans les contextes italien et ibérique, et en Amérique latine. Il y aborde l’aspect théologique de cette histoire, à l’aide d’une partie de la production mémorialiste et des traités justificatifs produits par l’Ordre. Suit une analyse des missions de rédemption conduites par les religieux de l’Ordre, entre le dernier quart du XVIe siècle et le début du XVIIIe siècle. Concernant la procédure, l’auteur met en relief les contours juridiques et normatifs et souligne l’importance des raisons économiques et politiques qui étaient derrière eux. Quatre exemples de rédemptions de captifs sont ainsi abordés à-traves l’analyse de livres de comptabilité. L’étude sur une longue période, entre 1575 et 1723, permet à l’auteur de mettre en évidence les changements intervenus dans les rachats en ce qui concerne la procédure, le financement et l’usage des aumônes et de l’argent collecté. Le modus operandi des rédemptions mercédaires est ensuite comparé avec celui d’autres institutes, laïcs et étatiques, qui s’occupent du rachat des captifs dans les territoires italien et ibérique. Là encore les logiques économiques, les exigences politiques et les intérêts nationaux et locaux qui guidaient cette activité sont mis en avant.La thèse soutient que les religieux de l’ordre de la Merci ne furent pas totalement libres d’agir, selon les prérogatives dictées par son propre Ordre, mais qu’ils se trouvèrent étroitement vinculés à des instructions données par le gouvernement espagnol et par les sujets eux-mêmes, ces dernières étant les principaux financeurs des missions de rachats. Autrement dit, il apparaît que l’action humanitaire de ces religieux répondait, en réalité, plutôt à des logiques économiques et à des intérêts politiques (c’est pour ça qu’on y parle de « Raison d’État ») et non pas aux principes d’une charité chrétienne qui était indifférente aux frontières nationales. Pour cette raison, en partant de l’observatoire spécifique des rédemptions mercédaires, l’auteur arrive enfin à envisager que le commerce des captifs à l’époque moderne ait pu servir de «catalyseur» de processus bien plus longs et complexes, tandis que le progressif détachement des politiques d’assistance des États européennes de la dimension religieuse. Et, aussi, qu’il ait pu en quelque sorte accélérer la graduelle et controverse naissance de sentiments d’appartenance nationale, ceux-ci s’imposant, à la fin de l’époque moderne, au détriment d’autres, plus traditionnels, liés aux communautés confessionnellesThe aim of this work is to analyse the captives redemptions' mechanism, through the study of the specific case of Mercedarians ransoming expeditions to North Africa. We have compared this mechanism with the ones pursued by other ransoming institutions in the Italian and Iberian areas, in order to let economics logics and juridical laws emerge that regulated te ransoming process. After a general introduction on the principal aspects that phenomenon entailed, a chapter of the tesis is dedicated to the analysis of four redemption missions, conducted by the religious Order of Our Lady of Mercy during a period of a century and half, precisely between 1575 and 1723
Con l’obiettivo di far luce sulle dinamiche economiche e sui meccanismi istituzionali che regolavano il riscatto dei cristiani captivi in Maghreb nei secoli centrali dell’età moderna, l’autore si propone di ricostruire l’attività redentrice di uno dei protagonisti indiscussi di quel commercio: l’Ordine di Nostra Signora della Mercede. Al fine di illustrane le specificità, l’autore presenta dapprima un quadro complessivo del fenomeno dei riscatti di captivi tra i secoli XVI e XVIII, inserendolo nel più generale contesto del Mediterraneo e della guerra da corsa combattuta tra le sue sponde. Successivamente, traccia una storia sintetica dell’Ordine della Mercede e della sua diffusione e progressivo sviluppo nei contesti italiano e iberico - con un occhio anche alla realtà dell’America spagnola - e attenta all’aspetto teologico e alla trattatistica giustificativa prodotta dai Mercedari stessi. Analizza, poi, a livello procedurale le missioni di redenzione condotte dai religiosi dell’Ordine a cavallo tra il tardo Cinquecento e il primo Settecento, ne traccia i contorni giuridici e normativi e mira a far emergere le ragioni economiche e politiche che le muovevano. A tal fine, prende in esame quattro esempi di redenzioni di captivi attraverso lo studio di altrettanti libri di conto: l’ampio arco cronologico di riferimento - un secolo e mezzo, dal 1575 al 1723 - consente all’autore di evidenziare i cambiamenti intercorsi a livello procedurale nei riscatti, così come in merito al loro finanziamento e alla destinazione d’uso delle elemosine di volta in volta raccolte. Il modus operandi delle redenzioni mercedarie è quindi messo a confronto con quello di altre istituzioni, laiche e statali, dedite al riscatto dei captivi in area italiana ed iberica e, anche qui, nell’intento di far emergere le logiche economiche, le istanze politiche e gli interessi nazionali e locali che vi sottostavano.La tesi difende l’idea che i religiosi della Mercede, nella loro opera della redenzione dei captivi, non fossero liberi di agire autonomamente e secondo le prerogative dettate dal proprio Ordine, ma che fossero, al contrario, strettamente vincolati a istruzioni date loro dal governo spagnolo e da privati cittadini, essendo questi ultimi i principali finanziatori delle loro missioni di riscatto. Sostiene, insomma, l’idea che l’azione umanitaria dei religiosi rispondesse, in realtà, più a logiche economiche e agli interessi della politica che non a quelli di una carità cristiana indifferente ai confini nazionali. Per tale ragione, l’autore, prendendo spunto dall’osservatorio specifico delle redenzioni mercedarie, giunge a ipotizzare che il commercio dei captivi in età moderna abbia potuto giocare un ruolo di «catalizzatore» di processi ben più ampi e complessi, come il progressivo distacco delle politiche assistenziali degli Stati dalla sfera religiosa, e che abbia potuto accelerare il graduale e controverso imporsi di sentimenti di appartenenza nazionale a scapito di altri, più tradizionali, legati alle comunità confessionali
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Sanon, Grégoire. "La politique des programmes télévisuels en Afrique Noire francophone : originalité ou rançon d'une assistance étrangère ? : cas du Burkina Faso et de la côte d'Ivoire." Paris 1, 1997. http://www.theses.fr/1997PA010588.
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Depuis la fin des années 1980, l’Afrique vit son tournant de la communication audiovisuelle. Après l'éveil de la presse écrite privée, on assiste à la création de radiodiffusions en FM et à l'arrivée des télévisions directes par satellites. Ces transformations du paysage audiovisuel suscitent des inquiétudes et l'on pense qu'avec l'intrusion des satellites, le continent noir court le risque de perdre son territoire de communication. Les craintes ne se fondent pas sur l'audience de ces nouveaux medias. N'est-ce pas en réalité la question des télévisions nationales qu'elles indexent ? C'est au lendemain des indépendances de 1960 que la télévision a été implantée en Afrique. La Côte d'Ivoire qui, comme le Burkina, compte parmi les pionniers entendait l'utiliser pour soutenir l'éducation au développement. Le Burkina misait de son cote sur le prestige qu'elle pouvait apporter a une nation indépendante. Dans les deux cas, la télévision s'est révélée un média inadapté aux milieux et aux fonctions qu'on lui prêtait. Elle est restée un outil d'information et de distraction qui doit la pérennité de sa diffusion à la coopération culturelle étrangère. C'est au titre de cette coopération que la France a créé canal France international (CFI) en 1989 pour fournir des programmes gratuits aux télévisions d’Afrique noire francophone. CFI vient s'ajouter à la présence des banques de programmes américains "worldnet" et allemands "transtel". Elles apportent des solutions à la pénurie d'images mais elles contribuent à étouffer les initiatives de production nationale et à exacerber l'absence de programmes nationaux sur le petit écran. Ces banques condamnent les programmateurs africains à gérer une politique des programmes télévisuels attelée à l'assistance étrangère. L'explosion actuelle des pratiques vidéo et la course aux antennes paraboliques au Burkina et en Côte d'Ivoire sont à considérer comme des avatars de cette politique d'accoutumance.
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Emery, Arnaud. "L'otage en sauvetage : étude juridique." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSE3006.
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Les prises d’otages sont nées le jour où l’homme a compris qu’il pouvait manipuler le lien émotionnel unissant deux individus afin de les forcer à lui céder une contrepartie. Forme de criminalité aussi ancienne que complexe, la prise d’otage fascine autant qu’elle inquiète depuis que les victimes sont régulièrement sacrifiées sur l’autel du conflit opposant ravisseurs et autorités négociatrices. À l’inverse de l’impact médiatique hors-norme qu’elles génèrent, ces crises semblent susciter une relative indifférence auprès des juristes et de la doctrine. Ce sujet qui semble échapper au droit touche pourtant à sa raison d’être : la protection du plus faible, la recherche du bien commun et de la paix. Ces travaux de recherches essaient de poser les jalons d’une réflexion juridique sur les questions allant de l’usage de la force armée en opération de sauvetage à la légalité des rançons en passant par la négociation de crise ou le rôle du juge. Les hypothèses émises sont systématiquement confrontées à l’avis des opérateurs rencontrés dans le cadre de ces travaux. In fine l’auteur pose un regard prospectif sur le cadre juridique entourant les opérations de sauvetage d’otage. À travers ce prisme cette thèse questionne les limites de l’État de droit et les appareils antiterroristes de nos sociétésHostage-taking began when man realized that he could manipulate the emotional bond between two individuals in order to force their hand and obtain an advantage. Hostage-taking is a crime extremely old and complex. It has started to fascinate our societies so much since victims have begun to be regularly sacrificed by kidnappers and negotiating authorities alike. Unlike the extraordinary media frenzy they generate, these crises seem to arouse relative indifference among lawyers and doctrine. This subject, which seems to elude the law, touches on its raison d'être: the protection of the weakest, the search for the common good and peace.This research work attempts to lay the groundwork for legal reflection on issues ranging from the use of armed force in rescue operations, to the legality of ransoms, to crisis negotiation and the role of the judge. The hypotheses put forward are systematically compared with the opinions of the operators met in the course of this work. Finally, the author takes a forward-looking look at the legal framework surrounding hostage rescue operations. Through this prism, this thesis questions the limits of the rule of law and the anti-terrorist apparatus of our societies
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Moussaileb, Routa. "Log analysis for malicious software detection." Thesis, Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2020. http://www.theses.fr/2020IMTA0211.
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Les rançongiciels demeurent la menace informatique principale pour les particuliers, les entreprises et les gouvernements. Les conséquences de ces attaques peuvent causer des pertes irréversibles si les exigences des attaquants ne sont pas satisfaites à temps. Cette thèse cible les rançongiciels Windows. Ils affectent les données des utilisateurs sauvegardées sur les ordinateurs ainsi que de nombreux services publics. Quatre étapes de l’attaque des rançongiciels sont définies : infection, déploiement, destruction et transaction. Les contre-mesures sont regroupées selon les techniques utilisées et attribuées à chaque phase de l'attaque. Cette thèse présente trois contributions. Le premier mécanisme de détection est situé dans la couche du système de fichiers. Il est basé sur la traversée du système qui permet d’exposer les comportements malveillants. Cette thèse propose également une analyse du trafic réseau. Les échantillons sont collectés pour une détection au niveau des paquets. Une étude des notes de rançon est faite pour situer la contre-mesure réseau dans l'étape appropriée de l’intrusion. La dernière contribution donne un aperçu des attaques, particulièrement des Doxware. Un modèle de quantification qui explore le système de fichiers Windows à la recherche de données importantes est présenté et complémenté par les pots de miels pour protéger les fichiers sensibles. Enfin, cette thèse offre des perspectives permettant d'établir un meilleur plan d’action pour les chercheursRansomware remains the number one cyberthreat for individuals, enterprises, and governments. Malware’s aftermath can cause irreversible casualties if the requirements of the attackers are not met in time. This thesis targets Windows ransomware. It affects users’ data and undermines many public services. Four stages of this malware attack are defined: delivery, deployment, destruction, and dealing. The corresponding countermeasures are assigned to each phase of the attack and clustered according to the techniques used. This thesis presents three contributions. The first detection mechanism is located in the file system layer. It is based on the system traversal that is sufficient to highlight the malicious behavior. This thesis proposes also an analysis of the network traffic. It is generated by collected ransomware samples to perform a packet-level detection. A study of the ransom notes is made to define where it takes place in a ransomware workflow. The last contribution provides an insight into plausible attacks, especially Doxware. A quantification model that explores the Windows file system in search of valuable data is presented. It is based on the term frequency-inverse document frequency solution provided in the literature for information retrieval. Honeypot techniques are also used to protect the sensitive files of the users. Finally, this thesis provides future perspectives granting a better roadmap for researchers
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Windisch, David. "Random walks, disconnection and random interlacements /." [S.l.] : [s.n.], 2009. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18343.
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Gleeson, James P. Saffman P. G. "Randon advection of a passive scalar /." Diss., Pasadena, Calif. : California Institute of Technology, 1999. http://resolver.caltech.edu/CaltechETD:etd-02062008-095449.
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Kang, Mihyun. "Random planar structures and random graph processes." Doctoral thesis, [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=985516585.
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Buckley, Stephen Philip. "Problems in random walks in random environments." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:06a12be2-b831-4c2a-87b1-f0abccfb9b8b.
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Recent years have seen progress in the analysis of the heat kernel for certain reversible random walks in random environments. In particular the work of Barlow(2004) showed that the heat kernel for the random walk on the infinite component of supercritical bond percolation behaves in a Gaussian fashion. This heat kernel control was then used to prove a quenched functional central limit theorem. Following this work several examples have been analysed with anomalous heat kernel behaviour and, in some cases, anomalous scaling limits. We begin by generalizing the first result - looking for sufficient conditions on the geometry of the environment that ensure standard heat kernel upper bounds hold. We prove that these conditions are satisfied with probability one in the case of the random walk on continuum percolation and use the heat kernel bounds to prove an invariance principle. The random walk on dynamic environment is then considered. It is proven that if the environment evolves ergodically and is, in a certain sense, geometrically d-dimensional then standard on diagonal heat kernel bounds hold. Anomalous lower bounds on the heat kernel are also proven - in particular the random conductance model is shown to be "more anomalous" in the dynamic case than the static. Finally, the reflected random walk amongst random conductances is considered. It is shown in one dimension that under the usual scaling, this walk converges to reflected Brownian motion.
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GOMES, CARMEN ANTUNES. "RANDON ACCESS WITH NOTIFICATION: MULTIPLE ACCESS PROTOCOLS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1993. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9396@1.
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FURNAS CENTRAIS ELÉTRICAS S.AEste trabalho propõe e analisa uma versão de um protocolo híbrido de acesso aleatório com notificação, desenvolvido para redes VSAT ( Very Small Aperture Terminal) onde se busca uma combinação do baixo tempo de resposta de protocolos do tipo RA-TDMA (Random Access-Time Division Multiple Access) . No protocolo aqui estudado as transmissões são feitas em uma primeira tentativa através de um esquema RA-TDMA e no caso de ocorrência de colisão, os pacotes envolvidos são retransmitidos através de um esquema DA-TDMA. As notificações de transmissões são feitas pelas estações VSAT, através de um canal de sinalização, onde é atribuído a cada uma delas um segmento de tempo, aqui referido como slot de tempo, de posição fixa dentro de cada quadro. O desempenho do protocolo é analisado utilizando a técnica de Análise no Ponto de Equilíbrio (EPA), sendo considerados como medida de desempenho os parâmetros retardo médio de mensagem, vazão e taxa de rejeição de pacotes. São consideradas mensagens de um pacote e mensagens de tamanho variável. Comparações com outros protocolos contendo buffer ou não, também analisados utilizando a técnica EPA, são realizadas. Resultados de simulação encontrados na literatura de dois outros protocolos são também apresentados.
A version of a random access with notification, multiple access protocol developed for VSAT networks is considered. This hybrid protocol combines the low response delay of RA- TDMA contention protocols with the efficiency and stability of DA-TDMA type protocols. In the considered protocol a message generated by a VSAT station is transmitted, in a first attempt, using a RA-TDMA type of scheme. If a collision occurs in this first transmission of the message the collided packets are retransmitted through a Demand Assignment (DA)-TDMA type of access. When a remote station transmits its message in a RA-TDMA contention mode it notifies the central hub using a separate TDMA channel in which a fixed position time slot is reserved to each station within a frame. The performance of the protocol is evaluated in terms of throughput, expected delay and packet rejection rate by means of the so called Equiilibrium Point Analysis (EPA). Single and multi-packet messages, with a random number of packets, are considered in the performance analysis. Comparisons with other hybrid protocols, which were also evaluated in the literature by means of the EPA technique or through simulation results, are presented.
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Ngoc, Anh Do Hoang. "Anomalous diffusion and random walks on random fractals." Doctoral thesis, Universitätsbibliothek Chemnitz, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-201000205.
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The purpose of this research is to investigate properties of diffusion processes
in porous media. Porous media are modelled by random Sierpinski carpets,
each carpet is constructed by mixing two different generators with the same
linear size. Diffusion on porous media is studied by performing random
walks on random Sierpinski carpets and is characterized by the random walk
dimension $d_w$.
In the first part of this work we study $d_w$ as a function of the ratio of constituents
in a mixture. The simulation results show that the resulting $d_w$ can
be the same as, higher or lower than $d_w$ of carpets made by a single constituent
generator. In the second part, we discuss the influence of static external
fields on the behavior of diffusion. The biased random walk is used to model
these phenomena and we report on many simulations with different field
strengths and field directions. The results show that one structural feature
of Sierpinski carpets called traps can have a strong influence on the observed
diffusion properties. In the third part, we investigate the effect of diffusion
under the influence of external fields which change direction back and forth
after a certain duration. The results show a strong dependence on the period
of oscillation, the field strength and structural properties of the carpet.
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Ogrowsky, Arne [Verfasser]. "Random Differential Equations with Random Delay / Arne Ogrowsky." München : Verlag Dr. Hut, 2011. http://d-nb.info/1017353352/34.
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Pymar, Richard James. "Random graphs and random transpositions on a circle." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610350.
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Park, Subok. "Signal detection with random backgrounds and random signals." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280729.
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In this dissertation we explore theoretical and computational methods to investigate Bayesian ideal observers for performing signal-detection tasks. Object models are used to take into account object variability in image backgrounds and signals for the detection tasks. In particular, lumpy backgrounds (LBs) and Gaussian signals are used for various paradigms of signal-detection tasks. Simplified pinhole imaging systems in nuclear medicine are simulated for this work. Markov-chain Monte Carlo (MCMC) methods that estimate the ideal observer test statistic, the likelihood ratio, for signal-known-exactly (SKE) tasks, where signals are nonrandom, are employed. MCMC methods are extended to signal-known-statistically (SKS) tasks, where signals are random. Psychophysical studies for the SKE and SKS tasks using non-Gaussian and Gaussian distributed LBs are conducted. The performance of the Bayesian ideal observer, the human observer, and the channelized-Hotelling observer for the SKE and SKS tasks is compared. Human efficiencies for both the SKE tasks and SKS tasks are estimated. Also human efficiencies for non-Gaussian and Gaussian-distributed LBs are compared for the SKE tasks. Finally, the theory of the channelized-ideal observer (CIO) is introduced to approximate the performance of the ideal observer by the performance of the CIO in cases where the channel outputs of backgrounds and signals are non-Gaussian distributed. Computational approaches to estimate the CIO are investigated.
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Hannigan, Patrick. "Random polynomials." Thesis, University of Ulster, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263248.
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Ball, Neville. "Random Structures." Thesis, Queen Mary, University of London, 2015. http://qmro.qmul.ac.uk/xmlui/handle/123456789/7902.
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For many combinatorial objects we can associate a natural probability distribution on the members of the class, and we can then call the resulting class a class of random structures. Random structures form good models of many real world problems, in particular real networks and disordered media. For many such problems, the systems under consideration can be very large, and we often care about whether a property holds most of the time. In particular, for a given class of random structures, we say that a property holds with high probability if the probability that that property holds tends to one as the size of the structures increase. We examine several classes of random structures with real world applications, and look at some properties of each that hold with high probability. First we look at percolation in 3 dimensional lattices, giving a method for producing rigorous confidence intervals on the percolation threshold. Next we look at random geometric graphs, first examining the connectivity thresholds of nearest neighbour models, giving good bounds on the threshold for a new variation on these models useful for modelling wireless networks, and then look at the cop number of the Gilbert model. Finally we look at the structure of random sum-free sets, in particular examining what the possible densities of such sets are, what substructures they can contain, and what superstructures they belong to.
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Horn, Florian. "Random Games." Paris 7, 2008. http://www.theses.fr/2008PA077235.
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Dans cette thèse, nous considérons les jeux comme un outil pour la synthèse de contrôleurs dans un système ouvert. Dans ce cadre, un jeu est défini par : une arène, sous la forme d'un graphe représentant les états et l'évolution du système; et une condition de victoire, représentant la spécification que le contrôleur doit garantir. Dans chaque état, la transition sortante est choisie soit par le contrôleur, soit par un environnement hostile, soit selon une loi stochastique. Ce processus est répété un nombre infini de fois, générant une partie infinie dont le vainqueur dépend de la condition de victoire. Nous étudions tout d'abord le cas fondamental des jeux d'accessibilité. Nous présentons une nouvelle approche pour en calculer les valeurs basée sur les permutations d'états aléatoires. En termes de complexité, cet "algorithme par permutations" est orthogonal aux algorithmes basés sur les stratégies : il est exponentiel dans le nombre d'états aléatoires, et non dans le nombre d'états contrôlés. Nous présentons également une heuristique d'amélioration pour cet algorithme, inspirée par l'algorithme d'amélioration de stratégies. Nous considérons ensuite la classe de problème très générale des jeux préfixe-indépendants. Nous prouvons l'existence de stratégie optimales pour ces jeux, et nous montrons que notre algorithme par permutations peut être étendu en un "méta-algorithme", transformant n'importe quel algorithme qualitatif en un algorithme quantitatif. Enfin, nous étudions les jeux de Muller, utilisant les "arbres de Zielonka" pour calculer la quantité de mémoire nécessaire et suffisante pour synthétiser une stratégie aléatoire "presque-sûrement" gagnanteIn this thesis, we study games as a tool for the synthesis of controllers for reactive Systems. In this setting, a game is defined by an arena, representing the System and its evolution as a graph; and a winning condition, which models the specification that the controller must ensure In each state, the choice of the outgoing transition is done by either Eve (the controller), Adam (an hostile environment), or Random (uncontrollable evolution obeying a stochastic law). This process is repeated for an infinite number of times, leading to an infinite play whose winner depends on the winning condition. Our first object of study is the simplest case of Computing the optimal values of reachability games. We present a new effective approach, based on permutations of random states, to solve this classical problem. In terms of complexity, the resulting "permutation algorithm" is orthogonal to the classical, strategy-based algorithms: it is exponential in the number of random states, rather than in the number of controlled states. We also present an improvement heuristic for this algorithm, inspired by the "strategy improvement" algorithm. We turn next to a much more general class of problems, covering ail fie cases where the winning condition is prefix-independent. We prove the existence of optimal strategies for these games, and show that our permutation algorithm can be extended into a "meta-algorithm", changing any qualitative algorithm into a quantitative algorithm. Lastly, we study the complexity of optimal strategies for regular winning conditions represented as Muller games, and especially the amount of memory that can be saved by using randomised strategies. Using the Zielonka tree, we show tight bounds on the necessary and sufficient memory needed to define randomised optimal strategies for any single Muller condition
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Dou, Carl C. Z. (Carl Changzhu). "Studies of random walks on groups and random graphs." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13243.
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Carigi, Giulia. "On the recurrence of random walks in Lévy random environments." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10088/.
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This thesis investigates one-dimensional random walks in random environment whose transition probabilities might have an infinite variance. The ergodicity of the dynamical system ''from the point of view of the particle'' is proved under the assumptions of transitivity and existence of an absolutely continuous steady state on the space of the environments. We show that, if the average of the local drift over the environments is summable and null, then the RWRE is recurrent. We provide an example satisfying all the hypotheses.
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Seierstad, Taral Guldahl. "The phase transition in random graphs and random graph processes." Doctoral thesis, [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=985760044.
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Käsmä, E. (Emilia). "Siis jotain random tutkimuksia ne voi tehdä:vierassanan random käyttö suomessa." Bachelor's thesis, University of Oulu, 2018. http://urn.fi/URN:NBN:fi:oulu-201802081181.
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Tutkin kandidaatintutkielmassani englannista peräisin olevan random-vierassanan käyttöä suomessa. Keskityn erityisesti sanan ominaisuuksien tarkasteluun lausekekontekstissa, sillä nuoren lainasanan syntaktisten ominaisuuksien tutkiminen antaa paljon tietoa sanan käytöstä kohdekielessä. Aineistoni sisältää 472 lausekekonteksteissaan esiintyvää random-sanan sananmuotoa, jotka olen seulonut Suomi24-sivustolta kerätystä korpuksesta. Analysoin lausekkeita konstruktioina, joissa random saa erilaisia merkityksiä riippuen siitä, millaisessa konstruktiossa ja millä paikalla se esiintyy. Aineistoni jakaantuu yhdeksään erilaiseen konstruktioon, joissa random-sana voi esiintyä niin edussanana kuin laajennuksenakin. Random-sanan merkitys ja sanaluokkastatus vaihtelevat konstruktion mukaan. Yleisimmin random-sanaa käytetään aineistossani taipumattomana adjektiivimääritteenä, jolloin random ei kongruoi lausekkeen edussanan mukaan. Myös adverbikäyttö on yleistä: silloin random esiintyy adessiivin tai essiivin yksikössä ja kuvaa tapaa. Random toimii usein myös lauseen subjektina tai objektina ja on tällöin substantiivi. Random-sanan käyttö suomessa on siis hyvin moninaista, ja käytön selvittäminen antaa tietoa paitsi sanasta, myös uusien lainasanojen käyttäytymisestä suomen kielessä.
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ORABY, TAMER. "Spectra of Random Block-Matrices and Products of Random Matrices." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1209391815.
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Wu, Lei. "Random inscribed polytopes." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3210646.
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Thesis (Ph. D.)--University of California, San Diego, 2006.Title from first page of PDF file (viewed June 7, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 60-65).
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Renlund, Henrik. "Reinforced Random Walk." Thesis, Uppsala University, Department of Mathematics, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-121389.
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Aghaee, Saeed. "Random Stream Cipher." Thesis, Växjö University, School of Mathematics and Systems Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:vxu:diva-1511.
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Stream ciphers are counted as an important part of symmetric encryption method. Their basic idea comes from One-Time-Pad cipher using XOR operator on the plain text and the key to generate the cipher. The present work brings a new idea in symmetric encryption method, which inherits stream key generation idea from synchronous stream cipher and uses division instead of xoring. The Usage of division to combine the plain text with stream key gives numerous abilities to this method that the most important one is using random factors to produce the ciphers.
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Xu, Su Huai. "Random analytic signals." Thesis, University of Macau, 2009. http://umaclib3.umac.mo/record=b1944056.
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Johansson, Carl Fredrik. "Random Loewner Chains." Doctoral thesis, KTH, Matematik (Inst.), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12163.
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This thesis contains four papers and two introductory chapters. It is mainly devoted to problems concerning random growth models related to the Loewner differential equation. In Paper I we derive a rate of convergence of the Loewner driving function for loop-erased random walk to Brownian motion with speed 2 on the unit circle, the Loewner driving function for radial SLE(2). Thereby we provide the first instance of a formal derivation of a rate of convergence for any of the discrete models known to converge to SLE. In Paper II we use the known convergence of (radial) loop-erased random walk to radial SLE(2) to prove that the scaling limit of loop-erased random walk excursion in the upper half plane is chordal SLE(2). Our proof relies on a version of Wilson’s algorithm for weighted graphs together with a Beurling-type hitting estimate for random walk excursion. We also establish and use the convergence of the radial SLE path to the chordal SLE path as the bulk point tends to a boundary point. In the final section we sketch how to extend our results to more general domains. In Paper III we prove an upper bound on the optimal Hölder exponent for the chordal SLE path parameterized by capacity and thereby establish the optimal exponent as conjectured by J. Lind. We also give a new proof of the lower bound. Our proofs are based on sharp estimates of moments of the derivative of the inverse SLE map. In particular, we improve an estimate of G. F. Lawler. In Paper IV we consider radial Loewner evolutions driven by unimodular Lévy processes. We rescale the hulls of the evolution by capacity, and prove that the weak limit of the rescaled hulls exists. We then study a random growth model obtained by driving the Loewner equation with a compound Poisson process with two real parameters: the intensity of the underlying Poisson process and a localization parameter of the Poisson kernel which determines the jumps. A particular choice of parameters yields a growth process similar to the Hastings-Levitov HL(0) model. We describe the asymptotic behavior of the hulls with respect to the parameters, showing that growth tends to become localized as the jump parameter increases. We obtain deterministic evolutions in one limiting case, and Loewner evolution driven by a unimodular Cauchy process in another. We also show that the Hausdorff dimension of the limiting rescaled hulls is equal to 1.
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Ray, Gourab. "Hyperbolic random maps." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/48417.
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Random planar maps have been an object of utmost interest over the last
decade and half since the pioneering works of Benjamini and Schramm, Angel and Schramm and Chassaing and Schaeffer. These maps serve as models
of random surfaces, the study of which is very important with motivations
from physics, combinatorics and random geometry.
Uniform infinite planar maps, introduced by Angel and Schramm, which
are obtained as local limits of uniform finite maps embedded in the sphere,
serve as a very important discrete model of infinite random surfaces. Recently, there has been growing interest to create and understand hyperbolic
versions of such uniform infinite maps and several conjectures and proposed
models have been around for some time. In this thesis, we mainly address
these questions from several viewpoints and gather evidence of their existence and nature.
The thesis can be broadly divided into two parts. The first part is
concerned with half planar maps (maps embedded in the upper half plane)
which enjoy a certain domain Markov property. This is reminiscent of that
of the SLE curves. Chapters 2 and 3 are mainly concerned with classi cation
of such maps and their study, with a special focus on triangulations. The
second part concerns investigating unicellular maps or maps with one face
embedded in a high genus surface. Unicellular maps are generalizations of
trees in higher genera. The main motivation is that investigating such maps
will shed some light into understanding the local limit of general maps via
some well-known bijective techniques. We obtain certain information about
the large scale geometry of such maps in Chapter 4 and about the local limit
of such maps in Chapter 5.Science, Faculty of
Mathematics, Department of
Graduate
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Forghani, Behrang. "Transformed Random Walks." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32538.
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We consider transformations of a given random walk on a countable group determined by Markov stopping times. We prove that these transformations preserve the Poisson boundary. Moreover, under some mild conditions, the asymptotic entropy (resp., rate of escape) of the transformed random walks is equal to the asymptotic entropy (resp., rate of escape) of the original random walk multiplied by the expectation of the corresponding stopping time. This is an analogue of the well-known Abramov's formula from ergodic theory.
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Thomack, Andrew. "Random Harmonic Polynomials." Thesis, Florida Atlantic University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10681500.
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The study of random polynomials and in particular the number and behavior of zeros of random polynomials have been well studied, where the first signicant progress was made by Kac, finding an integral formula for the expected number of zeros of real zeros of polynomials with real coefficients. This formula as well as adaptations of the formula to complex polynomials and random fields show an interesting dependency of the number and distribution of zeros on the particular method of randomization. Three prevalent models of signicant study are the Kostlan model, the Weyl model, and the naive model in which the coefficients of the polynomial are standard Gaussian random variables.
A harmonic polynomial is a complex function constructed by summing an analytic polynomial with a conjugated analytic polynomial. Li and Wei adapted the Kac integral formula for the expected number of zeros to study random harmonic polynomials and take particular interest in their interpretation of the Kostlan model. In this thesis we find asymptotic results for the number of zeros of random harmonic polynomials under both the Weyl model and the naive model as the degree of the harmonic polynomial increases. We compare the findings to the Kostlan model as well as to the analytic analogs of each model.
We end by establishing results which lead to open questions and conjectures about random harmonic polynomials. We ask and partially answer the question, “When does the number and behavior of the zeros of a random harmonic polynomial asymptotically emulate the same model of random complex analytic polynomial as the degree increases?” We also inspect the variance of the number of zeros of random harmonic polynomials, motivating the work by the question of whether the distribution of the number of zeros concentrates near its mean as the degree of the harmonic polynomial increases.
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Anderson, Grant. "Random Relational Rules." The University of Waikato, 2008. http://hdl.handle.net/10289/2562.
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In the field of machine learning, methods for learning from single-table data have received much more attention than those for learning from multi-table, or relational data, which are generally more computationally complex. However, a significant amount of the world's data is relational. This indicates a need for algorithms that can operate efficiently on relational data and exploit the larger body of work produced in the area of single-table techniques. This thesis presents algorithms for learning from relational data that mitigate, to some extent, the complexity normally associated with such learning. All algorithms in this thesis are based on the generation of random relational rules. The assumption is that random rules enable efficient and effective relational learning, and this thesis presents evidence that this is indeed the case. To this end, a system for generating random relational rules is described, and algorithms using these rules are evaluated. These algorithms include direct classification, classification by propositionalisation, clustering, semi-supervised learning and generating random forests. The experimental results show that these algorithms perform competitively with previously published results for the datasets used, while often exhibiting lower runtime than other tested systems. This demonstrates that sufficient information for classification and clustering is retained in the rule generation process and that learning with random rules is efficient. Further applications of random rules are investigated. Propositionalisation allows single-table algorithms for classification and clustering to be applied to the resulting data, reducing the amount of relational processing required. Further results show that techniques for utilising additional unlabeled training data improve accuracy of classification in the semi-supervised setting. The thesis also develops a novel algorithm for building random forests by making efficient use of random rules to generate trees and leaves in parallel.
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Desruisseaux, Bernard. "Random dynamic fonts." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0007/MQ29682.pdf.
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Desruisseaux, Bernard. "Random dynamic fonts." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27307.
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This thesis presents a general method and structure for storing, representing and reproducing random dynamic fonts, i.e., fonts whose each rendition of each letterform differs. Such fonts allow, e.g., to come closer to simulating true handwriting, by rendering its freedom, spontaneity, and unpredictability.This method allows the generation of random letterforms with different overall shapes, derived from single letterform descriptions, according to specified parameters and constraints. Letterforms generated in this manner remain closely related--to a certain extent--to the original letterforms, and preserve the continuity and thickness of the strokes.
Several examples of a typeface family designed with this method, implemented as PostScript Type 3 font programs, are presented. A survey of the literature on random dynamic fonts is also proposed.
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Makai, Tamas. "Random graph processes." Thesis, Royal Holloway, University of London, 2012. http://repository.royalholloway.ac.uk/items/b24b89af-3fc1-4d2f-a673-64483a3bc2f2/8/.
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This thesis deals with random graph processes. More precisely it deals with two random graph processes which create H -free graphs. The first of these processes is the random H-elimination process which starts from the complete graph and in every step removes an edge uniformly at random from the set of edges which are found in a copy of H. The second is the H-free random graph process which starts from the empty graph and in every step an edge chosen uniformly at random from the set of edges which when added to the graph would not create a copy of H is inserted. We consider these graph processes for several classes of graphs H, for example strictly two balanced graphs. The class of strictly two balanced graphs includes among others cycles and complete graphs. We analysed the H-elimination process, when H is strictly 2-balanced. For this class we show the typical number of edges found at the end of the process. We also consider the sub graphs created by the process and its independence number. We also managed to show the expected number of edges in the H -elimination pro- cess when H = Ki, the graph created from the complete graph on 4 vertices by removing an edge and when H = K34 where K34 is created from the complete bi- partite graph with 3 vertices in one partition and'4 vertices in the second partition, by removing an edge. In case of the H -free process we considered the case when H is the triangle and showed that the triangle-free random graph process only creates sparse subgraphs. Finally we have improved the lower bound on the length of the K34-free random graph process. '
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Goldschmidt, Christina Anna. "Large random hypergraphs." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615618.
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Croydon, David Alexander. "Random fractal dendrites." Thesis, University of Oxford, 2006. http://ora.ox.ac.uk/objects/uuid:4e17aebc-456d-4891-8527-692331ebff05.
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Dendrites are tree-like topological spaces, and in this thesis, the physical characteristics of various random fractal versions of this type of set are investigated. This work will contribute to the development of analysis on fractals, an area which has grown considerably over the last twenty years. First, a collection of random self-similar dendrites is constructed, and their Hausdorff dimension is calculated. Previous results determining this quantity for random self-similar structures have often relied on the scaling factors being bounded uniformly away from zero. However, using a percolative argument, and taking advantage of the tree-like structure of the sets considered here, it is shown that this condition is not necessary; a simple condition on the tail of the distribution of the scaling factors at zero is all that is assumed. The scaling factors of these recursively defined structures form what is known as a multiplicative cascade, and results about the height of this random object are also obtained. With important physical and probabilistic applications, the heat equation has justifiably received a substantial amount of attention in a variety of settings. For certain types of fractals, it has become clear that a key factor in estimating the heat kernel is the volume growth with respect to the resistance metric on the space. In particular, uniform polynomial volume growth, which occurs for many deterministic self-similar fractals, immediately implies uniform (on-diagonal) heat kernel behaviour. However, in the random fractal setting, this is frequently not the case, and volume fluctuations are often observed. Motivated by this, an analysis of how volume fluctuations lead to corresponding heat kernel fluctuations for measure-metric spaces equipped with a resistance form is conducted here. These results apply to the aforementioned random self-similar dendrites, amongst other examples. The continuum random tree (CRT) of Aldous is an important random example of a measure-metric space, and fits naturally into the framework of the previous paragraph. In this thesis, quenched (almost-sure) volume growth asymptotics for the CRT are deduced, which show that the behaviour in almost-every realisation is not uniform. Applying the results introduced above, these yield heat kernel bounds for the CRT, demonstrating that heat kernel fluctuations occur almost-surely. Finally, a new representation of the CRT as a random self-similar dendrite is presented.
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Gassend, Blaise L. P. (Blaise Laurent Patrick) 1978. "Physical random functions." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/37606.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 87-89).
In general, secure protocols assume that participants are able to maintain secret key information. In practice, this assumption is often incorrect as an increasing number of devices are vulnerable to physical attacks. Typical examples of vulnerable devices are smartcards and Automated Teller Machines. To address this issue, Physical Random Functions are introduced. These are Random Functions that are physically tied to a particular device. To show that Physical Random Functions solve the initial problem, it must be shown that they can be made, and that it is possible to use them to provide secret keys for higher level protocols. Experiments with Field Programmable Gate Arrays are used to evaluate the feasibility of Physical Random Functions in silicon.
by Blaise L.P. Gassend.
S.M.
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Pacheco, Carlos Ph D. Massachusetts Institute of Technology. "Directed random testing." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53297.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 155-162).
Random testing can quickly generate many tests, is easy to implement, scales to large software applications, and reveals software errors. But it tends to generate many tests that are illegal or that exercise the same parts of the code as other tests, thus limiting its effectiveness. Directed random testing is a new approach to test generation that overcomes these limitations, by combining a bottom-up generation of tests with runtime guidance. A directed random test generator takes a collection of operations under test and generates new tests incrementally, by randomly selecting operations to apply and finding arguments from among previously-constructed tests. As soon as it generates a new test, the generator executes it, and the result determines whether the test is redundant, illegal, error-revealing, or useful for generating more tests. The technique outputs failing tests pointing to potential errors that should be corrected, and passing tests that can be used for regression testing. The thesis also contributes auxiliary techniques that post-process the generated tests, including a simplification technique that transforms a, failing test into a smaller one that better isolates the cause of failure, and a branch-directed test generation technique that aims to increase the code coverage achieved by the set of generated tests. Applied to 14 widely-used libraries (including the Java JDK and the core .NET framework libraries), directed random testing quickly reveals many serious, previously unknown errors in the libraries. And compared with other test generation tools (model checking, symbolic execution, and traditional random testing), it reveals more errors and achieves higher code coverage.
(cont.) In an industrial case study, a test team at Microsoft using the technique discovered in fifteen hours of human effort as many errors as they typically discover in a person-year of effort using other testing methods.
by Carlos Pacheco.
Ph.D.
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Gómez, Silvio Normey. "Random forests estocástico." Pontifícia Universidade Católica do Rio Grande do Sul, 2012. http://hdl.handle.net/10923/1598.
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Previous issue date: 2012In the Data Mining area experiments have been carried out using Ensemble Classifiers. We experimented Random Forests to evaluate the performance when randomness is applied. The results of this experiment showed us that the impact of randomness is much more relevant in Random Forests when compared with other algorithms, e. g., Bagging and Boosting. The main purpose of this work is to decrease the effect of randomness in Random Forests. To achieve the main purpose we implemented an extension of this method named Stochastic Random Forests and specified the strategy to increase the performance and stability combining the results. At the end of this work the improvements achieved are presented.
Na área de Mineração de Dados, experimentos vem sendo realizados utilizando Conjuntos de Classificadores. Estes experimentos são baseados em comparações empíricas que sofrem com a falta de cuidados no que diz respeito à questões de aleatoriedade destes métodos. Experimentamos o Random Forests para avaliar a eficiência do algoritmo quando submetido a estas questões. Estudos sobre os resultados mostram que a sensibilidade do Random Forests é significativamente maior quando comparado com a de outros métodos encontrados na literatura, como Bagging e Boosting. O proposito desta dissertação é diminuir a sensibilidade do Random Forests quando submetido a aleatoriedade. Para alcançar este objetivo, implementamos uma extensão do método, que chamamos de Random Forests Estocástico. Logo especificamos como podem ser alcançadas melhorias no problema encontrado no algoritmo combinando seus resultados. Por último, um estudo é apresentado mostrando as melhorias atingidas no problema de sensibilidade.
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Gnacik, Michal. "Quantum random walks." Thesis, Lancaster University, 2014. http://eprints.lancs.ac.uk/69946/.
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In this thesis we investigate the convergence of various quantum random walks to quantum stochastic cocycles defined on a Bosonic Fock space. We prove a quantum analogue of the Donsker invariance principle by invoking the so-called semigroup representation of quantum stochastic cocycles. In contrast to similar results by other authors our proof is relatively elementary. We also show convergence of products of ampliated random walks with different system algebras; in particular, we give a sufficient condition to obtain a cocycle via products of cocycles. The CCR algebra, its quasifree representations and the corresponding quasifree stochastic calculus are also described. In particular, we study in detail gauge-invariant and squeezed quasifree states. We describe repeated quantum interactions between a `small' quantum system and an environment consisting of an infinite chain of particles. We study different cases of interaction, in particular those which occur in weak coupling limits and low density limits. Under different choices of scaling of the interaction part we show that random walks, which are generated by the associated unitary evolutions of a repeated interaction system, strongly converge to unitary quantum stochastic cocycles. We provide necessary and sufficient conditions for such convergence. Furthermore, under repeated quantum interactions, we consider the situation of an infinite chain of identical particles where each particle is in an arbitrary faithful normal state. This includes the case of thermal Gibbs states. We show that the corresponding random walks converge strongly to unitary cocycles for which the driving noises depend on the state of the incoming particles. We also use conditional expectations to obtain a simple condition, at the level of generators, which suffices for the convergence of the associated random walks. Limit cocycles, for which noises depend on the state of the incoming particles, are also obtained by investigating what we refer to as `compressed' random walks. Lastly, we show that the cocycles obtained via the procedure of repeated quantum interactions are quasifree, thus the driving noises form a representation of the relevant CCR algebra. Both gauge-invariant and squeezed representations are shown to occur.
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Hlavacek, Magda L. "Random Tropical Curves." Scholarship @ Claremont, 2017. http://scholarship.claremont.edu/hmc_theses/95.
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In the setting of tropical mathematics, geometric objects are rich with inherent combinatorial structure. For example, each polynomial $p(x,y)$ in the tropical setting corresponds to a tropical curve; these tropical curves correspond to unbounded graphs embedded in $\R^2$. Each of these graphs is dual to a particular subdivision of its Newton polytope; we classify tropical curves by combinatorial type based on these corresponding subdivisions. In this thesis, we aim to gain an understanding of the likeliness of the combinatorial type of a randomly chosen tropical curve by using methods from polytope geometry. We focus on tropical curves corresponding to quadratics, but we hope to expand our exploration to higher degree polynomials.
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Abdulsalam, Hanady. "Streaming Random Forests." Thesis, Kingston, Ont. : [s.n.], 2008. http://hdl.handle.net/1974/1321.
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Fox, Michael (Michael Robert) Carleton University Dissertation Mathematics. "Random alternative routing." Ottawa, 1994.
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Lautensack, Claudia. "Random Laguerre Tessellations." [S.l. : s.n.], 2007. http://digbib.ubka.uni-karlsruhe.de/volltexte/1000006484.
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Ghalloussi, Farah. "L'assurance des nouveaux risques maritimes." Thesis, Paris 1, 2019. http://www.theses.fr/2019PA01D021.
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L’émergence de nouveaux risques qui pèsent sur l’opération de transport maritime soulève la problématique de leur appréhension par le droit maritime et par les techniques de l’assurance. En effet, celle-ci étant la condition sine qua non de ce commerce, mérite que ses méthodes d’appréhension des nouveaux risques et ses procédés pour les prendre en charge soient questionnés pour voir dans quelle mesure ils peuvent faire l’objet d’une opération d’assurance. L’hostilité du milieu maritime est donc accentuée par l’instabilité du cadre réglementaire international, les incertitudes liées à la navigation dans certaines zones, le cumul des valeurs en risques sur les navires de très grandes dimensions et enfin la transition numérique mal maîtrisée de l’industrie maritime. D’abord, à travers l’identification des nouveaux risques qui préoccupent les opérateurs maritimes, il a pu être dégagé quelques traits communs dans leur appréhension. L’assurabilité technique et juridique de chacun de ces nouveaux risques est questionnée à la lumière de ses caractéristiques. Celui-ci est observé pour voir quelles vulnérabilités il crée, quelles peuvent être les conséquences de sa réalisation et quels défis il représente pour le marché de l’assurance. De plus, l’examen de l’encadrement juridique et normatif des nouveaux risques maritimes permet d’évaluer la pertinence des réponses élaborées pour leur gestion et le cas échéant proposer des réponses adaptées afin d’améliorer leur assurabilité quand cela est possible. Ensuite, l’assurance des nouveaux risques maritimes revient à garantir les risques sélectionnés par les parties contractantes parmi l’ensemble des risques assurables ou situés « à la limite de l’assurabilité ». Le principe de l’offre de garantie en la matière suit deux dynamiques liées l’une à l’autre. D’un côté, les assurés, incapables de faire face aux nouveaux risques, cherchent à les transférer aux assureurs en poussant ces derniers à étendre leur panel d’offres en créant des produits toujours plus spécifiques à leurs nouveaux besoins. D’un autre côté, les assureurs ont toujours accompagné leurs clients en repoussant les limites de leurs engagements et en augmentant leurs capacités de souscription en cherchant des solutions sur des marchés traditionnels ou alternatifs de transfert et de partage du risque. La mise en œuvre de la garantie souscrite doit permettre l’indemnisation des nouveaux risques réalisés contre lesquels l’acteur maritime s’est assuré. La mobilisation de la garantie d’assurance en cas de sinistre peut rencontrer des obstacles qui placent l’assureur maritime au centre de trois actions portant sur le contrat d’assurance maritime. Deux actions peuvent être déclenchées à son encontre : L’une par l'assuré, l’action en garantie, l’autre par la victime, l’action directe du tiers lésé. L’assureur maritime, qui a indemnisé son assuré pour le dommage qu’il a subi, dispose d’un recours contre le tiers responsable ayant mobilisé sa garantie par le biais de la subrogationThe rise of new risks that affect maritime transport operations raises the challenge of how to deal with them through maritime law and insurance procedures. Indeed, since it is the sine qua non condition of this trade, it is worth querying its methods of apprehending new risks and its procedures for dealing with them to see to what extent they can be the subject of an insurance operation. The hostility of the maritime environment is therefore intensified by the instability of the international legal framework, the uncertainties associated with shipping in certain areas, the accumulation of values at risk on very large vessels and finally the poorly monitored digital transition in the maritime industry. First, through the identification of new risks that are of concern to maritime operators, it has been made possible to identify some common features in their apprehension. The technical and legal insurability of each of these new risks is examined in the light of itscharacteristics. It is monitored to see what weaknesses it creates, what the consequences of its realization may be and what challenges it represents for the insurance market. In addition, the examination of the legal and normative framework for new maritime risks makes it possible to assess the relevance of the responses developed for their management and, if necessary, to propose appropriate responses in order to improve their insurability when this is possible. Next, the insurance of new maritime risks is to cover the risks selected by the contracting parties from among all insurable risks or those located "at the limit of insurability". The principle of the guarantee offer in this area follows two interdependent dynamics. On the one hand, policyholders, unable to cope with new risks, are seeking to transfer them to insurers by pushing them to expand their range of offers by creating products that are increasingly specific to their new needs. On the other hand, insurers have always been there for their clients by pushing the limits of their commitments and increasing their subscription capacities by seeking solutions in traditional or alternative risk transfer and sharing markets. The implementation of the guarantee taken out must make it possible to indemnify the new risks incurred against which the maritime actor has taken out insurance. The mobilization of insurance protection in the event of a claim may face barriers that place the marine insurer at the center of three actions dealing with the marine insurance contract. Two actions can be taken against him: One by the insured, the action in warranty, the other by the victim, the direct action taken by a third party against the insurer. The marine insurer, which has indemnified its policyholder for the damage it has suffered, has recourse against the liable third party who has mobilized its coverage through subrogation
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fr, kaimanov@univ-rennes1. "Boundaries and Harmonic Functions for Random Walks with Random Transition Probabilities." ESI preprints, 2001. ftp://ftp.esi.ac.at/pub/Preprints/esi1085.ps.
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