L'objectiu bàsic d'aquesta tesi és l'estudi de la dinàmica a l'entorn de tors de dimensió baixa de sistemes hamiltonians analítics. Per aquest estudi l'eina fonamental és l'ús de formes normals al voltant d'aquests objectes.La formulació dels resultats d'aquesta memòria s'ha fet de manera adient per a la seva aplicació a models de mecànica celeste del món real. Per aquest motiu els resultats no es redueixen només al cas autònom, sinó que algun d'ells pren en consideració la possiblitat que les diferents perturbacions pugin dependre del temps de forma periòdica o quasiperiòdica. Aquests resultats s'apliquen per descriure la dinàmica d'alguns problemes d'interes per la Astronàutica. Per tant, els resultats obtinguts inclouen també aplicacions numèriques.Els resultats assolits en cadascun del capítols de la memòria es poden sintetitzar de la forma següent:Capítol 1.- Estudi de la dinàmica entorn d'un tor parcialment el.líptic d'un sistema Hamiltonià autònom. Es donen cotes inferiors pel temps de difusió entorn d'un tor totalment el.líptic, així com estimacions, en el cas general, de la densitat de tors invariants (de qualsevol dimensió) al voltant del tor inicial. Les estimacions en la velocitat de difusió i en la proximitat a 1 d'aquesta densitat, són exponencialment petites respecte la distància al tor inicial.Capítol 2.- Computació numèrica de formes normals al voltant d'òrbites periòdiques. Es desenvolupa un mètode per a calcular formes normals al voltant d'òrbites periòdiques el.líptiques de sistemes hamiltonians. Aquesta metodologia és aplicada numèricament a una òrbita periòdica del Problema Restringit de tres Cossos espaial. Els resultats d'aquest capítol es poden veure com una implementació numèrica del Capítol 1.Capítol 3.- Persistència de tors de dimensió baixa sota perturbacions quasiperiòdiques. Es mostra que un tor de dimensió baixa d'un sistema hamiltonià sotmès a una perturbació quasiperiòdica és pot continuar respecte el paràmetre perturbatiu, tot afegint a les freqüències bàsiques inicials les de la perturbació, excepte per un conjunt de mesura petita pel paràmetre. Al igual que en el Capítol 1 també s'estima la densitat de tors en el problema perturbat. En ambdós casos, les cotes obtingudes per la mesura dels tors pels qual no és possible provar existència són de tipus exponencialment petit.Apèndix. Es presenta un resultat obtingut de forma conjunta amb Rafael Ramírez-Ros sobre la reducció a coeficients constants de sistemes d'equacions lineals autònoms perturbats quasiperiòdicament. Es mostra que tal reducció és possible excepte un reste exponencialment petit en el tamany de la perturbació.

Scientific information is required to make environmental policy that will enhance and protect the health of ecosystems. The issues placed on the policy agenda come from the interactions amongst stakeholders, decision makers and other influential actors. These actors include government, civil society, private sector, and planning regimes. Ideally, scientific research then provides members of the policy community with assessed options upon which final decisions are eventually made. <br /><br /> This process is more complex than most in the realm of environmental policy because the goal of sustainability, commonly advocated by government, should serve to guide choices regarding policy alternatives. Sustainability, in practice, requires simultaneous attention to factors such as the needs of present and future generations; consideration for vastly differing social, environmental, and economic perspectives; and development of effective strategies to deal with the interconnectedness and complexity of the world. Management of these factors demands an ability to collect and process massive amounts of information at different temporal and spatial scales. The complexity of such situations means that there are instances when scientific information is not available and decisions need to be made quickly. <br /><br /> Using a case study approach, this thesis investigates the Canadian Wildlife Service?s attempts to achieve its mandate of conserving migratory birds while approving bismuth as an alternative to lead that was shown to cause poisoning of birds. This case study serves as an example of the tension between limited or ambiguous scientific information and urgent decisions. The chosen policy alternative to the use of lead shot was the approval of bismuth shot as a non-toxic substitute in 1997 and banning the use of lead shot nationwide in 1999. This decision to approve bismuth shot was based upon a few studies that were interpreted in a way that made it appear benign when compared to lead. This thesis examines the implications of this decision by conducting a comprehensive literature review of bismuth?s interactions with soil, vegetation, and animals, with some medical information on humans to put findings into an anthropocentric context. Also, analysis has been carried out on the results of a four-year study on bismuth in a wetland site near Kingston, Ontario, Canada. Finally, a ?post-normal perspective? exploration of the Canadian Wildlife Service revealed that decisions could be harmful to both human and environmental health if the values and knowledge of stakeholders are not taken into account and if uncertainties are overlooked. <br /><br /> Key findings generated by the literature review were potential chronic impacts to the neurological and reproductive health of animals exposed to bismuth shot. In turn, bismuth-contaminated meat may be a source of bismuth for humans and therefore guidelines for consumption should be investigated. Also, soil and vegetation have also been shown to accumulate bismuth, but it is unknown if it amounts to toxic levels. The wetland study helped to address the literature gap of bismuth?s fate in the environment. The mean concentration of bismuth in the soil after four years was 6. 40 µg/g, which was significantly higher than the control soil mean of 0. 42 µg/g. Ultimately, in terms of environmental policy, a ?post-normal perspective? offers three main tools for decision makers faced with urgent issues and uncertain facts. Namely, extended peer communities, acknowledgement and demonstration of uncertainty, and making values explicit.

Influenza A and B viruses are major causes of seasonal flu epidemics each year. Hemagglutinin (HA) mediates the binding of virus to host cell and the fusion with host membrane. The crystal of HA in complex with antibody that reveals the mechanism by which antibody recognizes HA may not diffract to high resolution, thereby preventing the accurate interpretation of the structural model. The application of normal mode refinement that aims for improving the structure quality at the low resolution is tested. These studies provide some guidelines for future refinement of HA-antibody complex structures. By comparing the residues constituting the base of the receptor binding site of influenza A and B virus HAs, it is found that they share some similarities, except for a Phe at position 95 of influenza B virus hemagglutinin (BHA) versus Tyr in of influenza A virus hemagglutinin (AHA). The recombinant protein BHA containing the F95Y mutation exhibits the increased receptor binding affinity and specificity. However, recombinant viruses with the Phe95Tyr mutation show lower erythrocyte agglutination titer and decreased binding abilities with different cell lines. The replication of the Phe95Tyr mutant virus in mice is also attenuated. These data suggest that the increased receptor binding ability of HA alone is not advantageous to the pathogenesis of the viruses. The structure of BHA2 (a portion of BHA near the C-terminus) at the post-fusion state has been determined to 2.45 Å resolution. This protein forms a hairpin-like conformation rich in -helices. About 70 residues from the N-terminus is a three-stranded coiled coil, and the remaining of the protein packs in anti-parallel against the groove formed by the central helices. In the post-fusion state of BHA2, the helix converted from the B-loop in pre-fusion state contacts the C-terminal fragment of this protein with more hydrophobic interactions as compared to AHA2. This structure illustrates the distinct stabilization strategy employed by BHA2 to form a post-fusion state that resembles that for AHA2. These studies will further the understanding of BHA with respect to its role in receptor binding ability and fusion.

Scientific information is required to make environmental policy that will enhance and protect the health of ecosystems. The issues placed on the policy agenda come from the interactions amongst stakeholders, decision makers and other influential actors. These actors include government, civil society, private sector, and planning regimes. Ideally, scientific research then provides members of the policy community with assessed options upon which final decisions are eventually made. <br /><br /> This process is more complex than most in the realm of environmental policy because the goal of sustainability, commonly advocated by government, should serve to guide choices regarding policy alternatives. Sustainability, in practice, requires simultaneous attention to factors such as the needs of present and future generations; consideration for vastly differing social, environmental, and economic perspectives; and development of effective strategies to deal with the interconnectedness and complexity of the world. Management of these factors demands an ability to collect and process massive amounts of information at different temporal and spatial scales. The complexity of such situations means that there are instances when scientific information is not available and decisions need to be made quickly. <br /><br /> Using a case study approach, this thesis investigates the Canadian Wildlife Service?s attempts to achieve its mandate of conserving migratory birds while approving bismuth as an alternative to lead that was shown to cause poisoning of birds. This case study serves as an example of the tension between limited or ambiguous scientific information and urgent decisions. The chosen policy alternative to the use of lead shot was the approval of bismuth shot as a non-toxic substitute in 1997 and banning the use of lead shot nationwide in 1999. This decision to approve bismuth shot was based upon a few studies that were interpreted in a way that made it appear benign when compared to lead. This thesis examines the implications of this decision by conducting a comprehensive literature review of bismuth?s interactions with soil, vegetation, and animals, with some medical information on humans to put findings into an anthropocentric context. Also, analysis has been carried out on the results of a four-year study on bismuth in a wetland site near Kingston, Ontario, Canada. Finally, a ?post-normal perspective? exploration of the Canadian Wildlife Service revealed that decisions could be harmful to both human and environmental health if the values and knowledge of stakeholders are not taken into account and if uncertainties are overlooked. <br /><br /> Key findings generated by the literature review were potential chronic impacts to the neurological and reproductive health of animals exposed to bismuth shot. In turn, bismuth-contaminated meat may be a source of bismuth for humans and therefore guidelines for consumption should be investigated. Also, soil and vegetation have also been shown to accumulate bismuth, but it is unknown if it amounts to toxic levels. The wetland study helped to address the literature gap of bismuth?s fate in the environment. The mean concentration of bismuth in the soil after four years was 6. 40 µg/g, which was significantly higher than the control soil mean of 0. 42 µg/g. Ultimately, in terms of environmental policy, a ?post-normal perspective? offers three main tools for decision makers faced with urgent issues and uncertain facts. Namely, extended peer communities, acknowledgement and demonstration of uncertainty, and making values explicit.

In this thesis we study algorithms for computing normal forms for matrices of Ore polynomials while controlling coefficient growth. By formulating row reduction as a linear algebra problem, we obtain a fraction-free algorithm for row reduction for matrices of Ore polynomials. The algorithm allows us to compute the rank and a basis of the left nullspace of the input matrix. When the input is restricted to matrices of shift polynomials and ordinary polynomials, we obtain fraction-free algorithms for computing row-reduced forms and weak Popov forms. These algorithms can be used to compute a greatest common right divisor and a least common left multiple of such matrices. Our fraction-free row reduction algorithm can be viewed as a generalization of subresultant algorithms. The linear algebra formulation allows us to obtain bounds on the size of the intermediate results and to analyze the complexity of our algorithms. We then make use of the fraction-free algorithm as a basis to formulate modular algorithms for computing a row-reduced form, a weak Popov form, and the Popov form of a polynomial matrix. By examining the linear algebra formulation, we develop criteria for detecting unlucky homomorphisms and determining the number of homomorphic images required.

This thesis presents a new algorithm for computing the Hermite form of a polynomial matrix. Given a nonsingular n by n matrix A filled with degree d polynomials with coefficients from a field, the algorithm computes the Hermite form of A in expected number of field operations similar to that of matrix multiplication. The algorithm is randomized of the Las Vegas type.

<p>Queueing models have been used extensively in the design of call centres. In particular, a queueing model will be used to describe a help desk which is a form of a call centre. The design of the queueing model involves modelling the arrival an service processes of the system.</p><p>Conventionally, the arrival process is assumed to be Poisson and service times are assumed to be exponentially distributed. But it has been proposed that practically these are seldom the case. Past research reveals that the log-normal distribution can be used to model the service times in call centres. Also, services may involve stages/tasks before completion. This motivates the use of a phase-type distribution to model the underlying stages of service.</p><p>This research work focuses on developing statistical models for the overall service times and the service times by job types in a particular help desk. The assumption of exponential service times was investigated and a log-normal distribution was fitted to service times of this help desk. Each stage of the service in this help desk was modelled as a phase in the phase-type distribution.</p><p>Results from the analysis carried out in this work confirmed the irrelevance of the assumption of exponential service times to this help desk and it was apparent that log-normal distributions provided a reasonable fit to the service times. A phase-type distribution with three phases fitted the overall service times and the service times of administrative and miscellaneous jobs very well. For the service times of e-mail and network jobs, a phase-type distribution with two phases served as a good model.</p><p>Finally, log-normal models of service times in this help desk were approximated using an order three phase-type distribution.</p>

Reporäntan som är Riksbankens viktigaste styrmedel används för att påverka landets inflation. Det har utförts omfattande undersökningar om ränteförändringar på den amerikanska marknaden. Flera forskare konstaterar att en höjning av reporäntan medför en nedgång av börskursen och vice versa samt att de finner skillnader branscherna emellan. Syfte med undersökningen är att studera om denna teori överensstämmer med den svenska aktiemarknaden. Studiens tidsperiod innefattar åren 2002 – 2011, detta för att få med både en hög- respektive lågkonjunktur, för att på så sätt undersöka om reporänteförändringen ger en starkare effekt under konjunktursvängningar. De urval som vi fokuserar på är branschindexen Finans-, Media-, Hälsa- samt Industri. En kvantitativ metod kommer att genomföras och datan inhämtas från Stockholmsbörsen OMX.  Metoden som används är en eventstudie vilket innebär att det utförs en analys av en händelse effekt. De slutsatser som vi kan dra utifrån våra resultat av beräkningarna är att det inte råder något samband mellan en ränteförändring och börskursen utifrån våra diagram av de generella höjningarna och sänkningarna. Men däremot belyser utfallet av våra hypoteser att det föreligger ett samband mellan ränteförändringar och aktiekursen. Det föreligger heller inga skillnader vad gäller branschkänsligheten mellan branschindexen. När det gäller konjunktursvängningarna fann vi att det förekom ett samband mellan höjningarna under högkonjunkturen samt sänkningarna under lågkonjunkturen. Orsaken till att effekten inte alltid är så tydlig på händelsedagen kan grunda sig i att allmänheten redan sen innan har hunnit rätta sig efter den nya informationen. Sammanfattningsvis är det svårt att förutsäga att marknaden är effektiv utifrån de resultat som vi har fått.

Shewhart X bar control charts with estimated control limits are widely used in practice. When the sample size is not fixed,we propose seven statistics to estimate the standard deviation sigma . These estimators are applied to estimate the control limits of Shewhart X bar control chart. The estimated results through simulated computation are given and discussed. Finally, we investigate the performance of the Shewhart X bar control charts based on the seven estimators of sigma via its simulated average run length (ARL).

Thesis (Ph. D.)--Oregon State University, 2003. / Typescript (photocopy). Includes bibliographical references (leaves 43-46). Also available on the World Wide Web.