Thèse de doctorat : Mathématiques et d'informatique. Mathématiques pures : Bordeaux 1 : 2008. / Titre provenant de l'écran-titre.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 102-111).

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

One of the major objectives in story understanding is to discover the causal reasoning behind characters' actions and to link these into an overall picture of the characters' motivations and actions. Thus the main aim when processing a sentence is to discover a character's goal in which this sentence can be considered as a step towards its achievement. The above process uses abductive reasoning in drawing its inferences and as a consequence of this any facts that are derived from a sentence might be invalid, causing a number of facts to be generated that are inconsistent with the knowledge base. A further complication to story understanding is that much of the information that is necessary for understanding to occur can only be obtained using default reasoning. Any such default fact remain valid unless a further statement proves that this is not the case. As a consequence of the above any new statements must be check against the rest of the knowledge base to make sure there are no inconsistencies and a list of supporting statements must be held so that any inconsistency found can be resolved and erased. An alternative to erasing these inconsistent statements within the knowledge base is to maintain a number of consistent environments using an assumption based truth maintenance system to enforce consistency. This has the advantage that more than one environment may be worked on at once and environments can be compared. The thesis discusses the maintenance of more than one environment and proposes a blackboard system, along with an assumption based truth maintenance system, as an ideal architecture to support the requirements of a story understanding program. The thesis also describes the knowledge sources, such as syntax and semantics, that are necessary for story understanding and how their operation should be controlled using a dynamic scheduling system.

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A point-weighted structure is an incidence structure with each point assigned an element of some set W C Z+ as a 'weight'. A point-weighted structure with no repeated blocks and the property that the sum of the weights of the points incident with anyone block is a constant k is called a point-weighted design. A t - (v, k, Aj W) point-weighted design is such a structure with the sum of the weights of all the points equal to v and the property that every set of t distinct points is incident with exactly A blocks. This thesis introduces and examines this generalisation of block designs. The first chapter introduces incidence structures and designs. Chapter 2 introduces and defines point-weighted designs. Three constructions of families of t - (v, k, Aj W) point-weighted designs are given. Associated with any point-weighted design is the incidence structure on which it is based - the 'underlying' incidence structure (u.i.s.). It is shown in Chapter 3 that any automorphism of the u.i.s. of a t - (v, k, Aj W) point-weighted design with more than one block and t > 1 preserves weights in the point-weighted design. The u.i.s. of such a point-weighted design is shown to be a block design if and only if every point is assigned the same weight. A necessary and sufficient condition is obtained for the assignment of weights in any point-weighted design to be essentially uniquely determined by the u.i.s. Chapter 4 considers t-{v, k, Aj W) point-weighted designs in which all of the points apart from a 'special' point have the same weight. It is shown that when v > k the weight of the special point is an integer multiple of the weight assigned to all the other points. A class of these point-weighted designs is demonstrated to be equivalent to a class of group-divisible designs with specific parameters. The final chapter uses the procedure of point-complementing incidence structures to construct point-weighted designs. Trivial point-weighted designs are defined and a necessary and sufficient condition for the existence of a member of a certain class of these is obtained. A correspondence between this class of point-weighted designs and certain trivial block designs is given using point-complementing.

Carbon steel finds much application for use in industries including civil; manufacturing; oil and gas; as well as, renewable energy. Common examples for usage of steel include water pipelines; oil pipelines; bridges; etc. The main advantages of steel over other engineering materials are its strength and affordability. However, steel undergoes corrosion which is a degradation mechanism that occurs as a result of the electrochemical interaction between steel and its environment. There are two main options to control corrosion, aside from material selection techniques, namely, the use of protective coating systems to isolate the steel from the environment; or the use of cathodic protection. Cathodic protection involves the use of galvanic anodes or impressed current system to prevent steel corrosion. Currently the oil and gas industry accounts for the major share of consumption of galvanic anodes for the protection of steel in engineering applications. Recent incursions into deep water depths by the Oil and Gas industry in the last decade or so has brought to the fore the need to understand better the performance of steel at deep and ultra deep water depths; as well as to develop an understanding of how cathodic protection works at these water depths. So far, the bulk of industry experience lies in shallow waters and current international cathodic protection design guidelines are based on data collated at these shallow water depths. It is the objective of this research work to assess the corrosion properties of steel with deep seawater parameters and determine design current density requirements for effective cathodic protection of steel at deep and ultra deep water depths offshore.

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

published_or_final_version / Computer Science / Doctoral / Doctor of Philosophy

This is chapter 1 of the book (first 25 pages of a book with 392 pages). How can an economy based on something as volatile as knowledge be sustained? The urgency of improving our understanding of a knowledge-based economy provides the context and necessity of this study. In a previous study entitled A Sociological Theory of Communications: The Self-Organization of the Knowledge-based Society (2001) the author specified knowledge-based systems from a sociological perspective. In this book, he takes this theory one step further and demonstrates how the knowledge base of an economic system can be operationalized, both in terms of measurement and by providing simulation models. Loet Leydesdorff (Ph.D. Sociology, M.A. Philosophy, and M.Sc. Biochemistry) reads Science and Technology Dynamics at the Amsterdam School of Communications Research (ASCoR), University of Amsterdam. He has published extensively in science and technology studies about the Triple Helix of university-industry-government relations, scientometrics, systems theory, social network analysis, and the sociology of innovation. He received the Derek de Solla Price Award for Scientometrics and Informetrics in 2003. In 2005, he held â The City of Lausanneâ Honor Chair at the School of Economics, Université de Lausanne, Switzerland. This interdisciplinary study provides both models of the knowledge base of an economy and instruments for its measurement, as applied to the German and Dutch economies in terms of regional and sectorial differences. The simulations introduce a set of algorithms for modeling various forms of anticipation in social networks. The knowledge base of an economy can be specified as a strongly anticipatory dynamic that operates at the supra-individual level.