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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Mordell-Weil Groups of Large Rank in Towers

Occhipinti, Thomas January 2010 (has links)
Let k be the algebraic closure of the field with q elements. We build upon recent work of Ulmer and Berger to give examples of elliptic curves and higher dimensional abelian varieties over the field K=k(t) with the property that their ranks become arbitrarily large when dth roots of the variable t are adjoined to K for d varying across the integers relatively prime to q. We also give a first example of an elliptic curve whose rank under such extensions grows linearly in d, for those d prime to q.
2

Sign Pattern Matrices and Semirings

Mohindru, Preeti 15 November 2011 (has links)
Sign pattern theory examines what can be said about a matrix if one knows the signs of all or some of its entries but not the exact values. Since all we know is the sign of each entry, we can write these sign patterns as matrices whose entries come from the set {+1, -1, 0, #}, where # is used for an unknown sign. Semirings satisfy all properties of rings with unity except the existence of additive inverses. The set {+1, -1, 0, #} can be viewed as a commutative semiring in natural way. In the thesis, we give a semiring version of the Cayley-Dickson construction which allows one to construct the sign pattern semiring from the Boolean semiring. We use tools from Boolean matrices to study sign nonsingular (SNS) matrices. We also investigate different notions of rank of matrices over semirings. For these rank functions we simplify proofs of classical inequalities for the sum and the product of matrices using the semiring versions of the Cauchy-Binet and Laplace theorems. For matrices over the sign pattern semiring, the minimum rank of the sign pattern is compared with the other versions of the rank. We also characterize irreducible powerful sign pattern matrices and investigate the period and base of an SNS matrix.
3

Nonparametric Tests for Umbrella Alternatives in Stratified Datasets

Larock, Josh 15 August 2023 (has links)
This thesis considers the problem of hypothesis testing for umbrella alternatives when there are two groups, or strata, of observations. The proposed methods extend a previously established general framework of hypothesis testing based on rankings to stratified datasets by first aligning the strata. The tests based on the Spearman and Kendall distances between ranking vectors lead to the traditional aligned-rank tests and new methods which account for “misalignment” under the alternative hypothesis. Asymptotic null distributions and simulation studies are given for the Spearman distance. Diagnostic tools for the misalignment issue are illustrated alongside the proposed tests on a dataset of IQ scores of coma patients. Extensions to three or more strata and ”adaptive” tests are provided as future research directions.
4

Ranks and Partial Cuts in Forward Hypergraphs

Sawilla, Reginald Elias 02 May 2011 (has links)
Many real-world relations are networks that can be modelled with a kind of directed hypergraph named a forward hypergraph (F-graph). F-graphs capture the semantics of both conjunctive and disjunctive dependency relations. Logic statements are sometimes represented using AND/OR directed graphs and they directly correspond with F-graphs; we provide algorithms to convert between the two types of graph. One problem of interest in networks is determining the degree to which the network, with a priority on certain elements, depends upon individual nodes. We address this problem by providing an algorithm, AssetRank, which computes vertex ranks and takes into account network priorities, preferential dependencies, and extra-network influences. A second problem of interest in networks is optimizing the removal of nodes to separate two subcommunities (source and target) to the greatest practical degree, even when a complete disconnection is impractical. The problem is complicated by the need to consider the cost of removing nodes, a budget that constrains the degree to which separation is possible, cascading effects of removing a node, non-linear effects of removing nodes in combination, and removing nodes with the greatest impact on the subcommunities. To this end, we use F-graphs and introduce the concepts of vertex closures and closure-relation graphs. We created two partial-cut algorithms: the first one computes an optimal solution to this NP-hard optimization problem, and the second one estimates an optimization by exploring the closure-relation graph in a best-first search manner. Computer network defence provides a ready application area. Network defenders wish to understand which services and hosts are defence priorities (defence goals), and then, which configurations and vulnerabilities are the most useful to attackers in reaching the defence goals. The defenders' resources are constrained in terms of available person-hours, finances, and acceptable impacts to operations. The work in this thesis supports network defenders by providing actionable information that efficiently removes attack enablers and ensures defence priorities. We present an integration of our algorithms with commercial and open-source network security software. / Thesis (Ph.D, Computing) -- Queen's University, 2011-04-30 22:17:52.062
5

The ownership of goods and cultures of consumption in Ludlow, Hereford and Tewkesbury, 1660-1760

Banks, Karen January 2014 (has links)
This thesis examines how the lifestyles of the middling sorts evolved during the period 1660 and 1760 as reflected in their relationship to material goods in three contrasting, but geographically near towns. The towns are similar to the degree that their history and circumstances led to them being viewed as backwaters, and this may have influenced consumption practices. Ludlow had lost its importance as the Capital of Wales; it stagnated until its fortunes began to be revived by achieving leisure town status. Hereford was a cathedral city and a county town, but was mainly poorly built and congested. It was locally, rather than nationally important. Tewkesbury was an inland port and a manufacturing centre, but it had been eclipsed by the larger and more successful cities of Bristol and Gloucester. This study of household goods in the middling interiors of Ludlow, Hereford and Tewkesbury between 1660 and 1760 set out first to investigate the extent to which the possessions of the middling ranks reflected their social status. The second aspect is to analyse the geographical spread of new goods in the three towns to determine the extent to which economic circumstances and location influenced consumption. Thirdly, the intention is to determine how status and politeness was expressed in the early modern home. Finally, this study aimed to ascertain what these factors could tell us about early modern consumers in the three towns. A sample of the domestic goods of the middling ranks from Ludlow, Hereford and Tewkesbury is examined and compared. The material culture of the three towns has previously attracted little academic interest. It is my intention that this thesis on the three towns complements and contributes to the existing bodies of work on early modern regional culture studies.
6

The economic evaluation of bus and minibus taxi terminals and transfer facilities

Pienaar, Wessel Johannes 12 1900 (has links)
Thesis (PhD (Civil Engineering))--University of Stellenbosch, 1998. / 147 leaves single sided printed, preliminary pages i-v and numbered pages 1-1 to 8-8. Includes bibliography,list of figures and tables. Digitized using a Hp Scanjet 8250 Scanner to pdf format (OCR). / ENGLISH ABSTRACT: The dissertation describes the functions of bus and minibus taxi terminals and transfer facilities. Planning, design and evaluation guidelines are proposed. These proposals are aimed at the following aspects: the geometric features and functional layout of facilities in order to enhance the effective usage thereof by passengers, as well as the smooth flow of vehicles; the location of facilities and traffic control arrangements, which take cognisance of effective traffic flow as well as acceptable walking distance by commuters; and an evaluation methodology which addresses allocative efficiency from an economic viewpoint, supplemented by analysis guidelines which consider distributive efficiency from a viewpoint of equitable distribution of welfare. It is explained how benefits for travellers, the transit operator and the subsidizing authority, and the opportunity costs of supplying the facility can be determined. A model is proposed whereby the non-monetary component of generalised travel costs can be estimated. The use of economic evaluation techniques for the selection and prioritisation of projects is detailed. This is supplemented by an example of an economic evaluation of a proposed bus/minibus taxi terminal. Subsequently it is examined how the design and effectiveness of a real world passenger transport terminal could be affected by the use of the guidelines proposed in the dissertation. The dissertation, lastly, deals with welfare distribution and the more equitable community accessibility and mobility which can be brought about by the creation and use of passenger transport terminals and transfer facilities. Also discussed is the accommodation of welfare distribution with an economic evaluation as a means of achieving greater equity or fairness and the ways in which this can be done. / AFRIKANSE OPSOMMING: Die proefskrif beskryf die funksies van bus- en minibustaxivervoereindpunte en oorstapfasiliteite. Beplannings-, ontwerp- en evalueringsriglyne word voorgestel. Die voorsteUe is gerig op die volgende aspekte: (1) Die geometriese en funksionele uitieg om die doeltreffende gebruik deur passasiers en vloei van voertuie te bevorder; (2) fasiliteitplasing en verkeersbeheermaatreels wat vlot voertuigbeweging sowel as aanvaarbare stapafstand in ag neem; en (3) 'n evalueringsmetodologie wat toewysingsdoeltreffendheid vanuit 'n ekonomiese oogpunt en verdelingsdoeltreffendheid vanuit 'n billike welvaartsverdelingsoogpunt in ag neem. Dit word verduidelik hoe voordele vir reisigers, die transit-operateur en die subsidierende owerheid, en die geleentheidskoste van fasiliteitsvoorsiening bepaal kan word. 'n Model word voorgestel waarvolgens die nie-monetere gedeelte van veralgemeende reiskoste beraam kan word. Die gebruik van ekonomiese evalueringstegnieke vir die keuse en prioritisering van projekte word verskaf. Dit word aangevul met 'n voorbeeld van 'n ekonomiese evaluering van 'n voorgestelde bus/minibustaxi-eindpunt. Vervolgens word dit ondersoek hoe die ontwerp en doeltreffendheid van 'n werklike passasiervervoereindpunt deur die gebruik van die voorgestelde riglyne beinvloed kan word. Ten slotte word welvaartverdeling en die groter toeganklikheid en beweeglikheid behandel wat binne 'n gemeenskap geskep kan word deur die voorsiening en gebruik van passasiersvervoereindpunte en oorstapfasiliteite. Dit word bespreek hoe 'n ekonomiese evaluering aangepas kan word as 'n maatreel om billikheid te bevorder.
7

Statistical model building and inference about the normalized site attenuation (NSA) measurements for electromagnetic interference (EMI)

Chiu, Shih-ting 09 August 2004 (has links)
Open site measurement on the electromagnetic interference is the most direct and universally accepted standard approach for measuring radiated emissions from an equipment or the radiation susceptibility of a component or equipment. A site is qualified for testing EMI or not is decided by the antenna measurements. In this work, we use data from setups with di erent factors to find relations of measurement and the situation of antenna. A one change point model has been used to fit observed measurements and compare the di erences with two kinds of antenna (broadband antenna and dipole antenna). However, with only one change point model it may not give a suitable fit for all data sets in this work. Therefore, we have tried other models and applied them to the data. Furthermore, we try to set up another standard more strict than ¡Ó4dB based on statistical inference results in deciding whether a site is a better one with more precision in measuring EMI values. Finally, a program by Matlab with a complete analysis based on the procedure performed here is provided, so that it may be used as a standard tool for evaluating whether a site is with good measurement quality in practice.
8

On the Robustness of the Rank-Based CUSUM Chart against Autocorrelation

Hackl, Peter, Maderbacher, Michael January 1999 (has links) (PDF)
Even a modest positive autocorrelation results in a considerable increase in the number of false alarms that are produced when applying a CUSUM chart. Knowledge of the process to be controlled allows for suitable adaptation of the CUSUM procedure. If one has to suspect the normality assumption, nonparametric control procedures such as the rank-based CUSUM chart are a practical alternative. The paper reports the results of a simulation study on the robustness (in terms of sensitivity of the ARL) of the rank-based CUSUM chart against serial correlation of the control variable. The results indicate that the rank-based CUSUM chart is less affected by correlation than the observation-based chart: The rank-based CUSUM chart shows a smaller increase in the number of false alarms and a higher decrease in the ARL in the out-of-control case than the the observation-based chart. (author's abstract) / Series: Forschungsberichte / Institut für Statistik
9

Senzorické hodnocení vybraného druhu masného výrobku v závislosti na výrobci. / Sensory evaluation of a selected type of a meat product produced by various producers.

VLČEK, Jiří January 2011 (has links)
The diploma thesis describes the issue of sensory evaluation of food and food products, in particular the sensory evaluation of a selected type of a meat product produced by various producers. Due to its great popularity with Czech consumers, ?Vysočina? salami was selected for the sensory evaluation. Six producers were randomly selected to undergo the testing. The evaluation was conducted in the laboratories of the Faculty of Agriculture of the University of South Bohemia. The testing was performed by 58 evaluators being the students and employees of the Faculty of Agriculture of the University of South Bohemia. For the purposes of the sensory evaluation, the method of a rank test was used for which each evaluator obtained one sample of the salami of each producer and was to rank the samples based on their quality from the best to the worst. Based on the sum of ranks, the following rank was determined: Vysočina Hodice, MP Krásno, Maso Planá, Kostelecké uzeniny, KMOTR ? Masna Kroměříž and Masna Příbram. In order to ascertain the demonstrativeness of differences among the evaluated samples, the Friedman?s method was used. The resultant value has shown that there are demostrative differences among the evaluated samples at the probability level of 99 %.
10

Rank Estimation in Elliptical Models : Estimation of Structured Rank Covariance Matrices and Asymptotics for Heteroscedastic Linear Regression

Kuljus, Kristi January 2008 (has links)
This thesis deals with univariate and multivariate rank methods in making statistical inference. It is assumed that the underlying distributions belong to the class of elliptical distributions. The class of elliptical distributions is an extension of the normal distribution and includes distributions with both lighter and heavier tails than the normal distribution. In the first part of the thesis the rank covariance matrices defined via the Oja median are considered. The Oja rank covariance matrix has two important properties: it is affine equivariant and it is proportional to the inverse of the regular covariance matrix. We employ these two properties to study the problem of estimating the rank covariance matrices when they have a certain structure. The second part, which is the main part of the thesis, is devoted to rank estimation in linear regression models with symmetric heteroscedastic errors. We are interested in asymptotic properties of rank estimates. Asymptotic uniform linearity of a linear rank statistic in the case of heteroscedastic variables is proved. The asymptotic uniform linearity property enables to study asymptotic behaviour of rank regression estimates and rank tests. Existing results are generalized and it is shown that the Jaeckel estimate is consistent and asymptotically normally distributed also for heteroscedastic symmetric errors.

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