De nos jours la protection des données numériques est un problème très important. Que ce soit pour des applications de confidentialité, de communication, de traçabilité ou d'identification par exemple, il est nécessaire de développer des techniques adaptées. Dans le cadre de cette thèse en collaboration avec la société STRATEGIES S.A., la méthode choisie pour la protection de maillages 3D est l'insertion de données cachées, également appelée tatouage numérique. Pour des données 3D, un des problèmes les plus importants est la phase de synchronisation qui intervient dans les algorithmes d'insertion et d'extraction des données. Cette phase permet de repérer, de sélectionner et d'ordonner les « zones » qui sont privilégiées pour la dissimulation d'information. Nous avons choisi d'orienter le manuscrit sur cette phase. Ainsi, nous proposons une classification des méthodes de tatouages en fonction de leur méthode de synchronisation. Puis en se basant sur des techniques de synchronisation par des structures de données, telle que les arbres couvrants de poids minimum, nous proposons une analyse théorique de cette structure. Dans un premier temps nous expliquons les raisons de la sensibilité des arbres à la mobilité des points. Puis connaissant ses faiblesses, nous proposons une autre technique de synchronisation toujours basée sur les arbres couvrants de poids minimum. / Data security is one of the main issue in computer science. We need to develop solutions for confidentiality, communication, fingerprinting or identification applications for exemple. In this thesis made with STRATEGIES S.A., the chosen method to protect 3D meshes is watermarking.Watermarking is divided in two steps, the embedding and the extraction. In both of them a synchronization phase is needed. It is one of the most important step for 3D mesh because it permits to look for areas available to embed information, and order them. All the thesis is devoted to the synchronization step. First of all, we propose a classification of watermarking techniques based on the type of synchronization method instead of evaluation criterions such as robustness or capacity.Then, from methods based on Euclidean minimum spanning tree, we propose a theoritical analysis of the mobility of the vertices in that kind of structure. First, we explain the reasons of the sensibility of the structure. Secondly, we propose another scheme based on the Euclidean minimum spanning tree knowing its fragility.

Cette thèse porte sur le polynôme de Tutte, étudié selon différents points de vue. Dans une première partie, nous nous intéressons à l’énumération des cartes planaires munies d’une forêt couvrante, ici appelées cartes forestières, avec un poids z par face et un poids u par composante non racine de la forêt. De manière équivalente, nous comptons selon le nombre de faces les cartes planaires C pondérées par TC(u + 1; 1), où TC désigne le polynôme de Tutte de C. Nous commençons par une caractérisation purement combinatoire de la série génératrice correspondante, notée F(z; u). Nous en déduisons que F(z; u) est différentiellement algébrique en z, c’est-à-dire que F satisfait une équation différentielle polynomiale selon z. Enfin, pour u ≥ -1, nous étudions le comportement asymptotique du n-ième coefficient de F(z; u). Nous observons une transition de phase en 0, avec notamment un régime très atypique en n-3 ln-2(n) pour u ϵ [-1; 0[, témoignant d’une nouvelle classe d’universalité pour les cartes planaires. Dans une seconde partie, nous proposons un cadre unificateur pour les différentes notions d’activités utilisées dans la littérature pour décrire le polynôme de Tutte.La nouvelle notion d’activité ainsi définie est appelée Δ-activité. Elle regroupe toutes les notions d’activité déjà connues et présente de belles propriétés, comme celle de Crapo qui définit une partition (adaptée à l’activité) du treillis des sous-graphes couvrants en intervalles. Nous conjecturons en dernier lieu que toute activité qui décrit le polynôme de Tutte et qui satisfait la propriété susmentionnée de Crapo peut être définie en termes de Δ-activités. / This thesis deals with the Tutte polynomial, studied from different points of view. In the first part, we address the enumeration of planar maps equipped with a spanning forest, here called forested maps, with a weight z per face and a weight u per non-root component of the forest. Equivalently, we count (with respect to the number of faces) the planar maps C weighted by TC(u + 1; 1), where TC is the Tutte polynomial of C.We begin by a purely combinatorial characterization of the corresponding generating function, denoted by F(z; u). We deduce from this that F(z; u) is differentially algebraic in z, that is, satisfies a polynomial differential equation in z. Finally, for u ≥ -1, we study the asymptotic behaviour of the nth coefficient of F(z; u).We observe a phase transition at 0, with a very unusual regime in n-3 ln-2(n) for u ϵ [-1; 0[, which testifiesa new universality class for planar maps. In the second part, we propose a framework unifying the notions of activity used in the literature to describe the Tutte polynomial. The new notion of activity thereby defined is called Δ-activity. It gathers all the notions of activities that were already known and has nice properties, as Crapo’s property that defines a partition of the lattice of the spanning subgraphs into intervals with respect to the activity. Lastly we conjecture that every activity that describes the Tutte polynomial and that satisfies Crapo’s property can be defined in terms of Δ-activity.

With the ubiquity of digitalization, digital convergence of applications, devices, networks and artifacts presents both challenges and opportunities for individuals, organizations and society. Physical artifacts that were not digital in the recent past are now increasingly becoming intertwined with digital components, providing them with digital capabilities. As a consequence, vast amounts of information that used to be invisible can now be captured, digitized and used in new places and novel ways. Organizations thus seek to innovate IT-enabled services based upon the flows of information across both internal and external organizational boundaries. Because IT-enabled services support organizational actors in communicating and collaborating both inside and outside the organizations’ boundaries, they can also assimilate and diffuse knowledge across these boundaries. The thesis is a collection of five papers and a cover paper reporting an exploration of the role of digitalized equipment in boundary-spanning practices as a contribution to the design and implementation of IT-enabled services. Three embedded case studies of Swedish industrial organizations provide an opportunity to address the research question. The findings are based on studies of remote diagnostics services for industrial equipment enabled by remote diagnostics systems, an application family within ubiquitous computing. The thesis illustrates that remote diagnostics systems have a profound impact on how organizational boundaries that were drawn as ‘cross-overs’ are becoming less limited by constraints of time, space and the type of data shared. These systems permit workers at remote sites to gain access to information about external dispersed equipment and production processes. They also create new boundaries between entities that were not previously connected and across existing boundaries with new information and knowledge. This thesis gives insight into how such information sharing across boundaries may leverage multicontextual practices. This thesis contributes to the existing literature with the development of a conceptual apparatus for understanding how embedded technology transforms boundary-spanning practices from a pure social activity to a boundary-spanning assemblage. Boundary spanning is an increasingly complex sociomaterial practice that fundamentally rests on technology as well as human competencies. The technology is deeply intertwined in the boundary-spanning activity as the sensors installed in the monitored equipment serve as the remote technicians’ eyes and ears. Together, the technology and the technicians form a boundary-spanning assemblage. While information systems research has called for attention to the ‘IT artifact’, this thesis underscores the importance of the characteristics of the specific technology and the profound effects it has had on its surroundings. In contrast to predominant ubiquitous computing research that mainly explores mobile applications, this thesis also shows how the increased embeddedness of IT makes technology an invisible but ever-present part of everyday work practices. Digitalized equipment with embedded technology thus raises not only novel opportunities but also novel challenges for both users and researchers. We can design IT solutions today where people close to the technology have no access to or awareness of it. People can be monitored without visual cues revealing the monitoring. Furthermore, developing or using an IT-enabled service is not merely about developing/using a technology or a system; it also involves issues about the technology’s value creation, its ownership, competencies and customer relationships. IT and services should thus not be considered as separate and subsequent processes: they are deeply intertwined and mutual. This thesis thus suggests that digitalized equipment with embedded technology deserves critical scrutiny.

Pattern recognition is an important area with potential applications in computer vision, Speech understanding, knowledge engineering, bio-medical data classification, earth sciences, life sciences, economics, psychology, linguistics, etc. Clustering is an unsupervised classification process corning under the area of pattern recognition. There are two types of clustering approaches: 1) Non-hierarchical methods 2) Hierarchical methods. Non-hierarchical algorithms are iterative in nature and. perform well in the context of isotropic clusters. Time-complexity of these algorithms is order of (0 (n) ) and above, Hierarchical agglomerative algorithms, on the other hand, are effective when clusters are non-isotropic. The single linkage method of hierarchical category produces a dendrogram which corresponds to the minimal spanning tree, conventional approaches are time consuming requiring O (n2 ) computational time. In this thesis we propose an intelligent partitioning scheme for generating the minimal spanning tree in the co-ordinate space. This is computationally elegant as it avoids the computation of similarity between many pairs of samples me minimal spanning tree generated can be used to produce C disjoint clusters by breaking the (C-1) longest edges in the tree. A systolic architecture has been proposed to increase the speed of the algorithm further. Simulation study has been conducted and the corresponding results are reported. The simulation package has been developed on DEC-1090 in Pascal. It is observed based on the simulation study that the parallel implementation reduces the time enormously. The number of processors required for the parallel implementation is a constant making the approach more attractive. Texture analysis and synthesis has been extensively studied in the context of computer vision, Two important approaches which have been studied extensively by researchers earlier are statistical and structural approaches, Texture is understood to be a periodic pattern with primitive sub patterns repeating in a particular fashion. This has been used to characterize texture with the help of the hierarchical data structure, tree. It is convenient to use a tree data structure as, along with the operations like merging, splitting, deleting a node, adding a node, etc, .it would be useful to handle a periodic pattern. Various functions like angular second moment, correlation etc, which are used to characterize texture have been translated into the new language of hierarchical data structure.

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This thesis addresses statistical estimation and testing of signals over a graph when measurements are noisy and high-dimensional. Graph structured patterns appear in applications as diverse as sensor networks, virology in human networks, congestion in internet routers, and advertising in social networks. We will develop asymptotic guarantees of the performance of statistical estimators and tests, by stating conditions for consistency by properties of the graph (e.g. graph spectra). The goal of this thesis is to demonstrate theoretically that by exploiting the graph structure one can achieve statistical consistency in extremely noisy conditions. We begin with the study of a projection estimator called Laplacian eigenmaps, and find that eigenvalue concentration plays a central role in the ability to estimate graph structured patterns. We continue with the study of the edge lasso, a least squares procedure with total variation penalty, and determine combinatorial conditions under which changepoints (edges across which the underlying signal changes) on the graph are recovered. We will shift focus to testing for anomalous activations in the graph, using the scan statistic relaxations, the spectral scan statistic and the graph ellipsoid scan statistic. We will also show how one can form a decomposition of the graph from a spanning tree which will lead to a test for activity in the graph. This will lead to the construction of a spanning tree wavelet basis, which can be used to localize activations on the graph.

Proximity problems and point set embeddability problems are fundamental and well-studied in computational geometry and graph drawing. Examples of such problems that are of particular interest to us in this dissertation include: finding the closest pair among a set P of points, finding the k-nearest neighbors to each point p in P, answering reverse k-nearest neighbor queries, computing the Yao graph, the Semi-Yao graph and the Euclidean minimum spanning tree of P, and mapping the vertices of a planar graph to a set P of points without inducing edge crossings. In this dissertation, we consider so-called kinetic version of these problems, that is, the points are allowed to move continuously along known trajectories, which are subject to change. We design a set of data structures and a mechanism to efficiently update the data structures. These updates occur at critical, discrete times. Also, a query may arrive at any time. We want to answer queries quickly without solving problems from scratch, so we maintain solutions continuously. We present new techniques for giving kinetic solutions with better performance for some these problems, and we provide the first kinetic results for others. In particular, we provide: • A simple kinetic data structure (KDS) to maintain all the nearest neighbors and the closest pair. Our deterministic kinetic approach for maintenance of all the nearest neighbors improves the previous randomized kinetic algorithm. • An exact KDS for maintenance of the Euclidean minimum spanning tree, which improves the previous KDS. • The first KDS's for maintenance of the Yao graph and the Semi-Yao graph. • The first KDS to consider maintaining plane graphs on moving points. • The first KDS for maintenance of all the k-nearest neighbors, for any k ≥ 1. • The first KDS to answer the reverse k-nearest neighbor queries, for any k ≥ 1 in any fixed dimension, on a set of moving points. / Graduate

大型災害頻傳傷亡慘重，若能把握於救災黃金72小時內救出受困民眾，則可望挽回更多寶貴的生命，但災區通訊網路基礎設施常因災害而遭受嚴重損毀，無法正常運作。救災工作在缺乏通訊系統的支援下，因溝通協調的困難而紊亂無章、效率低落。 本研究提出一個可快速恢復特定區域通訊服務的網路，並為其設計通訊的拓撲結構。我們稱該網路為應急蜂巢式行動通訊網路(Contingency Cellular Network)，簡稱CCN網路。CCN網路利用無線電連接災區行動電話網路中斷訊但結構未損的基地台建構而成，具有建置速度快、使用門檻低等多項特點，可支援災區救援的緊急通訊。 本研究中，我們以各毀損基地台通訊範圍內的通訊需求人數與災區毀損程度，作為效益參數，嘗詴在蜂巢式網路的格網架構以及數量有限的緊急通訊設備下，選擇效益較高的位置點配置緊急通訊設備，建立應急蜂巢式行動網路的網路拓撲，此拓撲除追求最大救災效益外，並顧及通訊品質，避免建立負載失衡的連線。我們將問題塑模為一類似圖論中的K-Minimum Cost Spanning Tree (K-Cardinality Tree or KCT)問題，稱為Depth Bounded K-Maximum Profit Spanning Tree問題，並提供數個快速的啟發式演算法，可在緊急時快速地建立應急蜂巢式行動網路拓撲。 / When a catastrophic natural disaster occurs, the efficiency of disaster response operation is critical to life saving. However, communication systems, such as cellular networks, usually crashed due to various causes that make coordination difficult for many disorganized disaster response workers extremely. Unfortunately, rapid deployment of many existing emergency communication systems relies on a good transportation system, which is usually not available in a catastrophic natural disaster. We propose a Contingency Cellular Network (CCN) by connecting disconnected base stations together with wireless links and portable power generators. CCN can support existing mobile phone users with limited capability. Such a system can support a large number of voluntary workers in the early hours of a catastrophic natural disaster, thus saving many lives. Communication traffics, either voice or data, are forwarded hop-by-hop to the external network that remains operational. The efficiency and effeteness of CCN is obviously depends on the topology of such a forwarding network. This thesis addresses the design of forwarding topology aiming to maximize its efficiency. We take the degree of emergency degree of the damage, population of each stricken as the priority measure as well as the amount of emergency recovery resources as the constraint to determine the topology. We model the CCN topology design problem into a Depth Bounded K-Maximum Spanning Tree Problem. The problem is proven NP-hard and we designed an efficient heuristic algorithm (DBTB) to solve it. We also model CCN topology design problem into a Hop Concerned K-Maximum Spanning iii Tree Program and designed a HCTB algorithm to solve it. The simulation results show that DBTB algorithm can control tree depth effectively but HCTB can gain more profit.

Metateams are both largely unexplored in the IS literature and economically important to major corporations and their IT vendors. Metateams are temporary groups composed of two or more geographically and inter-organisationally dispersed teams, commercially linked by project-specific agreements and enabled by electronic means of communication. Each one of these teams fulfils a particular and measurable objective, enshrined in the team's goal hierarchy and contractual obligations. The combination of efforts from every team in a metateam, contributes to achieving a common distant goal of project implementation. Thus, metateams are temporary teams (or groups) of distributed teams working across distance, firms, and cultures. In metateams, each participant team works with other teams on organisationally heterogeneous collaborative projects. Metateams are new and potentially powerful work structures resulting from the convergence of outsourcing, virtual organisations, and demands for global competitiveness. They promise to build IT solutions of high complexity, by integrating expertise from different fields and organisations. With the assistance of communication technologies, metateams can conquer barriers of time and space, enabling collaborative endeavours across a nation or across the globe. In a global business environment that demands innovation, flexibility, and responsiveness, metateams represent a revolution in the way organisations and practitioners do IT projects. However, as this study found, managing metateams presents unique difficulties due to conflicting demands arising from multiple realities. This dissertation presents an empirical research using a grounded theory approach that studies a major IT project performed by a metateam. The conceptual account emerges from an exploratory study of a major IT development and implementation project in the telecommunication industry. The project involved three key organisations and teams based in Australia, the Middle East, and Eastern Europe. The core pattern emerging from this study is one of constant conflict discovery and resolution, a process that progressively, and at a cost, allows the project to evolve from its initial incongruence into either a working solution or into project abandonment. This theory-building study presents a theoretical model, grounded on rich empirical data, interrelating key concepts of cost, conflict, communication, and trust, which serves to explain the pattern of actions and to propose a number of practical conclusions and recommendations. This research was guided by two key research objectives: (a) to add theoretical content to the understanding of key processes enacted by metateams in performing IT project work; and (b), to develop a framework that assists researchers and practitioners in predicting, explaining, and evaluating events and process associated with metateams. To the author's best knowledge, this study describes for the first time in the IS literature, the metateam organisation and the significant contextual issues they confront. In doing so, the study develops an understanding, grounded on rich empirical data from the substantive field of metateams. This new understanding contributes to both IS research and practice and provides guidance for future research.