La science moderne des graphes est apparue ces dernières années comme un domaine d'intérêt et a apporté des progrès significatifs à notre connaissance des réseaux. Jusqu'à récemment, les algorithmes d'exploration de données existants étaient destinés à des données structurées / relationnelles, alors que de nombreux ensembles de données nécessitent une représentation graphique, comme les réseaux sociaux, les réseaux générés par des données textuelles, les structures protéiques 3D ou encore les composés chimiques. Il est donc crucial de pouvoir extraire des informations pertinantes à partir de ce type de données et, pour ce faire, les méthodes d'extraction et d'analyse des graphiques ont été prouvées essentielles.L'objectif de cette thèse est d'étudier les problèmes dans le domaine de la fouille de graphes axés en particulier sur la conception de nouveaux algorithmes et d'outils liés à la diffusion d'informations et plus spécifiquement sur la façon de localiser des entités influentes dans des réseaux réels. Cette tâche est cruciale dans de nombreuses applications telles que la diffusion de l'information, les contrôles épidémiologiques et le marketing viral.Dans la première partie de la thèse, nous avons étudié les processus de diffusion dans les réseaux sociaux ciblant la recherche de caractéristiques topologiques classant les entités du réseau en fonction de leurs capacités influentes. Nous nous sommes spécifiquement concentrés sur la décomposition K-truss qui est une extension de la décomposition k-core. On a montré que les noeuds qui appartiennent au sous-graphe induit par le maximal K-truss présenteront de meilleurs proprietés de propagation par rapport aux critères de référence. De tels épandeurs ont la capacité non seulement d'influencer une plus grande partie du réseau au cours des premières étapes d'un processus d'étalement, mais aussi de contaminer une plus grande partie des noeuds.Dans la deuxième partie de la thèse, nous nous sommes concentrés sur l'identification d'un groupe de noeuds qui, en agissant ensemble, maximisent le nombre attendu de nœuds influencés à la fin du processus de propagation, formellement appelé Influence Maximization (IM). Le problème IM étant NP-hard, il existe des algorithmes efficaces garantissant l’approximation de ses solutions. Comme ces garanties proposent une approximation gloutonne qui est coûteuse en termes de temps de calcul, nous avons proposé l'algorithme MATI qui réussit à localiser le groupe d'utilisateurs qui maximise l'influence, tout en étant évolutif. L'algorithme profite des chemins possibles créés dans le voisinage de chaque nœud et précalcule l'influence potentielle de chaque nœud permettant ainsi de produire des résultats concurrentiels, comparés à ceux des algorithmes classiques.Finallement, nous étudions le point de vue de la confidentialité quant au partage de ces bons indicateurs d’influence dans un réseau social. Nous nous sommes concentrés sur la conception d'un algorithme efficace, correct, sécurisé et de protection de la vie privée, qui résout le problème du calcul de la métrique k-core qui mesure l'influence de chaque noeud du réseau. Nous avons spécifiquement adopté une approche de décentralisation dans laquelle le réseau social est considéré comme un système Peer-to-peer (P2P). L'algorithme est construit de telle sorte qu'il ne devrait pas être possible pour un nœud de reconstituer partiellement ou entièrement le graphe en utilisant les informations obtiennues lors de son exécution. Notre contribution est un algorithme incrémental qui résout efficacement le problème de maintenance de core en P2P tout en limitant le nombre de messages échangés et les calculs. Nous fournissons également une étude de sécurité et de confidentialité de la solution concernant la désanonymisation des réseaux, nous montrons ainsi la rélation avec les strategies d’attaque précédemment definies tout en discutant les contres-mesures adaptés. / Modern science of graphs has emerged the last few years as a field of interest and has been bringing significant advances to our knowledge about networks. Until recently the existing data mining algorithms were destined for structured/relational data while many datasets exist that require graph representation such as social networks, networks generated by textual data, 3D protein structures and chemical compounds. It has become therefore of crucial importance to be able to extract meaningful information from that kind of data and towards this end graph mining and analysis methods have been proven essential. The goal of this thesis is to study problems in the area of graph mining focusing especially on designing new algorithms and tools related to information spreading and specifically on how to locate influential entities in real-world networks. This task is crucial in many applications such as information diffusion, epidemic control and viral marketing. In the first part of the thesis, we have studied spreading processes in social networks focusing on finding topological characteristics that rank entities in the network based on their influential capabilities. We have specifically focused on the K-truss decomposition which is an extension of the core decomposition of the graph. Extensive experimental analysis showed that the nodes that belong to the maximal K-truss subgraph show a better spreading behavior when compared to baseline criteria. Such spreaders can influence a greater part of the network during the first steps of a spreading process but also the total fraction of the influenced nodes at the end of the epidemic is greater. We have also observed that node members of such dense subgraphs are those achieving the optimal spreading in the network.In the second part of the thesis, we focused on identifying a group of nodes that by acting all together maximize the expected number of influenced nodes at the end of the spreading process, formally called Influence Maximization (IM). The IM problem is actually NP-hard though there exist approximation guarantees for efficient algorithms that can solve the problem while obtaining a solution within the 63% of optimal classes of models. As those guarantees propose a greedy approximation which is computationally expensive especially for large graphs, we proposed the MATI algorithm which succeeds in locating the group of users that maximize the influence while also being scalable. The algorithm takes advantage the possible paths created in each node’s neighborhood to precalculate each node’s potential influence and produces competitive results in quality compared to those of baseline algorithms such as the Greedy, LDAG and SimPath. In the last part of the thesis, we study the privacy point of view of sharing such metrics that are good influential indicators in a social network. We have focused on designing an algorithm that addresses the problem of computing through an efficient, correct, secure, and privacy-preserving algorithm the k-core metric which measures the influence of each node of the network. We have specifically adopted a decentralization approach where the social network is considered as a Peer-to-peer (P2P) system. The algorithm is built based on the constraint that it should not be possible for a node to reconstruct partially or entirely the graph using the information they obtain during its execution. While a distributed algorithm that computes the nodes’ coreness is already proposed, dynamic networks are not taken into account. Our main contribution is an incremental algorithm that efficiently solves the core maintenance problem in P2P while limiting the number of messages exchanged and computations. We provide a security and privacy analysis of the solution regarding network de-anonimization and show how it relates to previously defined attacks models and discuss countermeasures.

A series of small- to moderate-sized earthquakes occurred in Arkansas, Oklahoma and Texas from 2010 to 2012, coinciding with the arrival of the EarthScope Transportable Array (TA). The data the TA recorded from those earthquakes provide a unique opportunity to study attenuation of the Lg phase in the mid-continent and Gulf Coastal region. The TA data reveal previously unrecognized regional variability of ground motion propagation in the central United States. A study of the Fourier amplitude spectra shows the Lg phase exhibiting strong attenuation for ray paths from Arkansas, southwest through the Ouachita Orogenic Belt and into central Texas, and south into the Gulf Coastal region. Less attenuation is seen in central Texas for ray paths extending directly south from Oklahoma, though attenuation remains strong along the Gulf Coast. In contrast, ray paths to the north, regardless of source location, exhibit very little attenuation, especially in northern Missouri and southern Iowa. Regression models that incorporate near-receiver (distance-independent) attenuation due to thick sediments in the Gulf Coastal Plain successfully reduce path-related bias in the regression residuals for stations near the Gulf Coast. Dividing the central United States into three regions (the Gulf Coastal Plain, the Great Plains and the Midwest) further reduced bias, and allowed for the development of Q models in the Gulf Coastal Plain and the Great Plains. In the Gulf Coastal Plain, the Q model for that part of the ray path through the basement, from the earthquake to the base of the sediment deposits below the receiver, was found to be Q=(295±11)*f^(0.645±0.029). The model for attenuation in the sediment section near the receiver in the Gulf Coastal Plain is Q=(72±6.7)*f^(0.32±0.06) (velocity through the sediments is unconfirmed but thought to be approximately 1 km/s). The Q model for the Great Plains is  Q=(692±61.3)*f^(0.43±0.07). The Midwest region exhibited extremely complicated behavior: the data indicate little or no attenuation of amplitudes in the frequency band from approximately 0.7 to 2.0 Hz. As a consequence, Q in the Midwest region in that frequency range could not be realistically determined. / Master of Science

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2007. / Includes bibliographical references (p. 194-197). / Oceanic spreading centers are sites of magmatic, tectonic, and hydrothermal processes. In this thesis I present experimental and seismological constraints on the evolution of these complex regions of focused crustal accretion and extension. Experimental results from drained, triaxial deformation experiments on partially molten olivine reveal that melt extraction rates are linearly dependent on effective mean stress when the effective mean stress is low and non-linearly dependent on effective mean stress when it is high. Microearthquakes recorded above an inferred magma reservoir along the TAG segment of the Mid-Atlantic Ridge delineate for the first time the arcuate, subsurface structure of a long-lived, active detachment fault. This fault penetrates the entire oceanic crust and forms the high-permeability pathway necessary to sustain long-lived, high-temperature hydrothermal venting in this region. Long-lived detachment faulting exhumes lower crustal and mantle rocks. Residual stresses generated by thermal expansion anisotropy and mismatch in the uplifting, cooling rock trigger grain boundary microfractures if stress intensities at the tips of naturally occurring flaws exceed a critical stress intensity factor. / (cont.) Experimental results coupled with geomechanical models indicate that pervasive grain boundary cracking occurs in mantle peridotite when it is uplifted to within 4 km of the seafloor. Whereas faults provide the high-permeability pathways necessary to sustain high-temperature fluid circulation, grain boundary cracks form the interconnected network required for pervasive alteration of the oceanic lithosphere. This thesis provides fundamental constraints on the rheology, evolution, and alteration of the lithosphere at oceanic spreading centers. / by Brian J. deMartin. / Ph.D.

Thesis (S.M.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences and the Woods Hole Oceanographic Institution), 2001. / Includes bibliographical references (leaves 44-48). / Megamullions in slow-spreading oceanic crust are characterized by smooth "turtle-back" morphology and are interpreted to be rotated footwalls of long-lived detachment faults. Megamullions have been analyzed in preliminary studies, but many questions remain about structural and tectonic details of their formation, in particular how the hanging wall develops in conjugate crust on the opposing side of the rift axis. This study compares the structure of an off-axis megamullion complex and its conjugate hanging wall crust on the Mid-Atlantic Ridge near 27 0N. Two megamullion complexes, an older (Ml) and younger (M2), formed successively on the west side of the rift axis in approximately the same location within one spreading segment. Megamullion M1 formed while the spreading segment had only one inside comer on the west flank, and megamullion M2 formed after the segment developed double inside corners west of the axis and double outside corners east of the axis. The older megamullion formed between -22.3 and -20.4 Ma, and the younger megamullion formed between -20.6 and -18.3 Ma; they are presently -200-300 km off-axis. Reconstruction poles of plate rotation were derived and plate reconstructions were made for periods prior to initiation of the megamullion complex (anomaly 6Ar, -22.6 Ma), after the termination of megamullion Ml and during the development of megamullion M2 (anomaly 5E, -19 9 Ma), and shortly following the termination of megamullion M2 (anomaly 5C, -17.6 Ma). These reconstructions were used to compare morphological and geophysical features of both flanks at each stage of the megamullions' development. Megamullion Ml's breakaway occurred at -22.3 Ma and slip along this detachment fault continued and propagated northward at -20.6 Ma to form the northern portion of M2. The exhumed footwall of megamullion M1 has weak spreading-parallel lineations interpreted as mullion structures on its surface, and it forms an elevated plateau between the enclosing segment boundaries (non-transform discontinuities). There was an expansion southward of the detachment fault forming megamullion M2 at -20.1 Ma. It either cut a new detachment fault through megamullion Ml, stranding a piece of megamullion Ml on the conjugate side (east flank), or it linked into the active detachment fault that was forming megamullion M1 or propagated into its hanging wall. The expanded detachment of megamullion M2 and the termination of megamullion M1 occurred during a time when the enclosing spreading segment roughly doubled in length and formed two inside corners. Megamullion M2 developed prominent, high-amplitude (-600 m) mullion structures that parallel the spreading direction for more than 20 km at each inside corner. Its detachment fault was abandoned - 18.6 Ma in the south and ~18.3 Ma in the north ... / by Amy R. McKnight. / S.M.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第19889号 / 医博第4138号 / 新制||医||1016(附属図書館) / 32966 / 京都大学大学院医学研究科医学専攻 / (主査)教授 古川 壽亮, 教授 髙橋 良輔, 教授 富樫 かおり / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

No description available.

Wave models are an integral part of coastal engineering due to their ability to quantify information that is either unobtainable or unavailable. However, these models rely heavily on the input of a directional wave spectrum that describes the variation of energy with frequency and direction. This study investigated how five methods for computing the directional wave spectrum perform within the nearshore spectral wave model, STWAVE. The results of the five experimental runs showed that overall, the greatest differences between spectra were observed in the significant wave height parameter. The mean wave direction showed greater differences at the offshore model domain boundary and lesser differences as the wave enters the nearshore; and the peak period had fewer differences at the boundary, but at the nearshore the differences were dependent upon the presence of wind forcing. Winds had a significant impact on observed differences between the spectra in the domain by dominating the wave field variation.

No description available.

Cavitation has been known for a long time to cause damages in spillways athydropower plants, aerators are therefore often implemented to prevent this.The majority of the hydropower plants in Sweden are installed in the northernpart of the country. In this environment, construction details like vents areexposed to rain, snow, leaves, and other difficult nature conditions for a majorpart of the year. It is therefore of interest to see what will happen if the ventsare sealed.Similar experiments have earlier been investigated at Vattenfall AB, oneof the largest energy companies in Sweden. The investigation consists ofcase studies with multiple variables, closed and open vents, low and highwater levels. The calculations are done with help from computational fluiddynamics and the goal is to see how parameters such as pressure, spreading,and horizontal length change when the aerator is sealed compared to open.The calculations were also carried out in a way so tests in the future can bedone by Vattenfall to validate the results from the computational simulations.The geometry of the hydropower plant is taken from a plant in Skellefteälvenin northern Sweden.

本研究で提案するマルチレート符号化法は、各ユーザが同じ通信路符号器を持つものの、符号器のパラメータ(Repeat Accumulate符号の繰り返し回数)と符号器に直列に連接する拡散列の長さを変化させることで、異なるレートの情報伝送を実現する、という方法である。通信路にガウス雑音が加算される場合、任意に低い誤り率の高信頼通信を可能にし、合計伝送レートを最大にする最適な通信路符号のパラメータと拡散長を理論解析で求める。 / In this dissertation, the same encoder is employed for each user, and different rate transmissions is realized by adjusting the parameter of the encoder. We analyze the decoding performances of our coding schemes, and obtain the optimal coding parameters, which gives the maximum sum rates and approach the theoretical limits of the channel. The proposed coding schemes support multimedia services, and avoid employing multiple channel encoders to implement the multi-rate transmission. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University