Doctor of Philosophy / Department of Mathematics / Yan S. Soibelman / The motivic Donaldson-Thomas theory of 2-dimensional Calabi-Yau categories can be induced from the theory of 3-dimensional Calabi-Yau categories via dimensional reduction. The cohomological Hall algebra is one approach to the motivic Donaldson-Thomas invariants. Given an arbitrary quiver one can construct a double quiver, which induces the preprojective algebra. This corresponds to a 2-dimensional Calabi-Yau category. One can further construct a triple quiver with potential, which gives rise to a 3-dimensional Calabi-Yau category. The critical cohomological Hall algebra (critical COHA for short) is defined for a quiver with potential. Via the dimensional reduction we obtain the cohomological Hall algebra (COHA for short) of the preprojective algebra. We prove that a subalgebra of this COHA consists of a semicanonical basis, thus is related to the generalized quantum groups. Another approach is motivic Hall algebra, from which an integration map to the quantum torus is constructed. Furthermore, a conjecture concerning some invariants of 2-dimensional Calabi-Yau categories is made. We investigate the correspondence between the A∞-equivalent classes of ind-constructible 2-dimensional Calabi-Yau categories with a collection of generators and a certain type of quivers. This implies that such an ind-constructible category can be canonically reconstructed from its full subcategory consisting of the collection of generators.

Master of Science / Department of Agricultural Economics / Kevin C. Dhuyvetter / Risk is an inevitable part of production agriculture. Price risk is especially a concern for cattle producers in the Midwest. Producers can curtail profit volatility, to an extent, through the utilization of price risk management strategies such as forward contracting, hedging, using put and call options, Livestock Risk Protection Insurance (LRP), as well as Livestock Gross Insurance (LGM) for feedlot cattle. Learning about such price risk management tools can be a daunting task. Kansas State University Extension created a computer based simulation workshop to assist them in teaching cattle producers about price risk management strategies. The simulation paralleled a lecture where participants learned of the price risk management strategies that are available. The simulation allowed the workshop participants to practice using the management strategies as they assumed the role of a feedlot or ranch manager in charge of marketing the operation's calves. In a cooperative effort with Iowa State University, Kansas State University presented the Cattle Risk Management Workshops across the state of Iowa. Participants were given pre-and posttests to measure the effectiveness of the workshop. The overall post-test scores were 25 percentage points higher than the pre-test scores. This research also discusses the interest and perceptions of cattle producers regarding price risk management strategies. The effectiveness of simulations as a teaching tool in helping producers learn about price risk management strategies is also reviewed. In addition, the various price risk management strategies available to producers, as well as seasonality of prices and basis are analyzed. This research also explains and estimates the LRP Feeder Cattle Basis Model. The LRP Feeder Cattle Basis Model was developed with the objective of assisting producers in forecasting LRP basis. The model was developed using similar methodology applied in the creation of a CME basis forecasting model developed by Kansas State University Extension and Custom Ag Solutions, Inc. The LRP Feeder Cattle Basis Model automatically adjusts for the LRP price adjustment factor applied to beef steer calves weighing less than 600 pounds, and beef heifers weighing 600-900 pounds. The LRP Feeder Cattle Basis Model explains 71.37 percent of the variation of LRP basis.

M.Ing. / This dissertation deals with the implementation of a Reliability Basis Optimisation Process for Eskom’s fossil fired Power Stations. This study comes about as a result of the situation that Eskom currently finds itself in. Eskom currently has a generating capacity of 41 000MW. It supplies 95% of South Africa’s power requirements and 45% of Africa’s power requirements. With the unprecedented economical growth that South Africa has experienced in the last five years, coupled with the economic recession of 2008/2009, Eskom has found itself in a precarious position in terms of power delivery. Eskom’s request for a 45% tariff increase in its Multi Price Determination (MYPD2) application to NERSA was turned down and a figure of 25% was awarded. Eskom’s current reserve margin is currently lies as less than 10%. With the funding restrains it now becomes difficult to replace machinery as it fails. The focus now shifts of carrying out effective maintenance. Eskom established the Asset Management Department with a view to ensure that the right maintenance was carried out. Within the Asset Management Department the Reliability Basis Optimisation (RBO) Process was established. The aim of the RBO stream is to improve the reliability and availability of the fossil fired Power Station. This dissertation looks at how the RBO process was developed and rolled out to the Power Stations. It also gives a brief overview of the Asset Management Improvement process to which the RBO process is the backbone.

Many econometric analyses of commodity futures over the years have been performed using spot or front month contract prices. Using such daily prices without the consideration of the associated contract traded volumes is slightly erroneous because, in reality, traders will typically trade the ‘most liquid’ contract, that is, the contract with the largest average daily volume (ADV). The reason for this is in order to gain the best price when buying or selling. If this ‘true’ time series is to be considered, a mapping procedure is required to account for the price jumps at the time when a trader trades out of the expiring contract and enters the new front month contract. A key finding was that this effect was significant, irrespective of the size of the price jump, sometimes referred to as basis or roll and also due to the accumulated roll over a number of years corresponding to multiple contracts. It was also found that the mapping procedure has a significant effect on the time series and should hence always be employed if the realistic traded time series is to be considered. Given this phenomenon, algorithmically-traded commodities futures must necessarily employ such time series when creating metrics or considering an econometric analysis. The key findings include the importance of diversification in algorithmically-traded portfolios, utilising the AOM and PSI metrics. The mapping of data sets to create realistic ‘live-traded’ time series was found to be significant, while the optimal day of roll over prior to contract expiry was found to be related to the trading volumes for certain commodities. Other key findings include the causalities and spillovers within the metals sector where various relationships are evident once the results were processed and analysed, both pre and post mapping. Interestingly, the key relationships including bidirectional volatility and shock spillovers between the four key metals existed when the unmapped data was used however, many of the feedbacks within these relationships was lost when the mapped data sets were considered. A significant finding was therefore the consistent differences in findings between mapped and unmapped data sets attributed to the optimisation or favourability of the models (whether econometric or algorithmic). This is due to the unmapped data including roll or basis (which the models are fitted to) taking into account the roll or basis and utilising them in finding relationships between data sets. In the mapped data set (the time series seen by traders) the roll or basis is accounted for and hence the relationships found stand in real-time trading situations. The differences in the results show how the effect of mapping can be significant with unmapped data sets displaying results which will not exist in a real time traded time series.

Les nombres p-adiques sont un analogue des nombres réels plus proche de l’arithmétique. L’avènement ces dernières décennies de la géométrie arithmétique a engendré la création de nombreux algorithmes utilisant ces nombres. Ces derniers ne peuvent être de manière générale manipulés qu’à précision finie. Nous proposons une méthode, dite de précision différentielle, pour étudier ces problèmes de précision. Elle permet de se ramener à un problème au premier ordre. Nous nous intéressons aussi à la question de savoir quelles bases de Gröbner peuvent être calculées sur les p-adiques. / P-Adic numbers are a field in arithmetic analoguous to the real numbers. The advent during the last few decades of arithmetic geometry has yielded many algorithms using those numbers. Such numbers can only by handled with finite precision. We design a method, that we call differential precision, to study the behaviour of the precision in a p-adic context. It reduces the study to a first-order problem. We also study the question of which Gröbner bases can be computed over a p-adic number field.

This thesis includes a literary, as well as an empirical study examining the degree to which congregations within the Nederduitsch Hervormde Kerk van Afrika took church growth into consideration in the planning and erection of church centres during the past ten years. The methodology of practical theology is reflected by means of three concepts, namely: understanding, explanation and change. This study focuses mainly on the first two concepts - expressed as the hermeneutical understanding and the empirical reality. The third concept could be examined in a further study, in conjunction with research already done in this study. The hermeneutical understanding or theory was researched with two focal points in mind, namely: the theological perspective - in which the emphasis was firstly on the identity of the Church in Christ and secondly on the calling of the Church, expressed in the missio Dei and discipleship. The other focal point was the Biblical ideal, as it appears in the Word and is interpreted by theological traditions. The second action in this methodology was the empirical measurement in order to verify whether this hermeneutical understanding in reality, was negotiated within the Nederduitsch Hervormde Kerk van Afrika. Apart from a few exceptions, the conclusion reached is that the Nederduitsch Hervormde Kerk van Afrika did not consider church growth in the planning and erection of its church centres. It also became clear that the Church’s calling is aimed internally and not externally and the Church does not fulfil its mission- and discipleship calling. / Dissertation (MA (Practical Theology))--University of Pretoria, 2007. / Practical Theology / unrestricted

Cette thèse suppose l’examen du contrôle de la Cour de cassation française et de la Cour de cassation italienne sur la motivation des jugements afin de voir dans quels objectifs et de quelle façon est utilisée la technique du manque de base légale. Cette recherche suppose en effet de rechercher la politique jurisprudentielle de la Cour de cassation française au regard de ce cas d’ouverture à cassation et de comparer avec l’évolution législative et jurisprudentielle en Italie, pays dans lequel peut se constater une érosion du contrôle de la motivation. En effet, suite à la réforme de l’été 2012, l’art. 360, alinéa 1°, n. 5, c.p.c. italien n’accorde plus aux parties la possibilité de se pourvoir en cassation en invoquant l’omission, l’insuffisance ou la contradiction de la motivation, mais dispose que le pourvoi en cassation n’est ouvert que pour défaut de considération d’un fait concluant pour la solution du litige et de nature controversée. Or, une telle réforme pose la question de la portée juridique de la nouvelle version de l’art. 360, alinéa 1°, n. 5, c.p.c.italien, étant nécessaire de savoir si en Italie l’insuffisance des motifs de fait donne est encore un motif d’ouverture à cassation. L'analyse de la technique au moyen de laquelle la Cour de cassation française garantit les parties contre l'exercice arbitraire du pouvoir judiciaire devient un instrument de recherche indispensable afin de trouver une solution interprétative qui permettra de continuer à dénoncer devant la Cour de cassation italienne l'utilisation - ou plutôt le non-examen - de maximes de l'expérience dans le cadre du nouvel art . 360 , par. 1 , n. 5 , c.p.c. italien. Cette analyse mettra en relief que les problématiques découlant du contrôle de la suffisance des motifs de fait sont différentes en Italie et en France. En Italie, cela soulève la question de la compatibilité de ce contrôle avec la fonction de cassation et de la portée juridique de l’art. 360, alinéa 1°, n. 5, c.p.c. En revanche, en France ces problèmes ne se profilent pas, même si se pose la question de l’usage politique du défaut de base légale. / This thesis involves the examination of the control of the French and Italian Highs Courts on the motivation of judgments in order to see what are the objectives and how is used the technique of the lack of legal basis. It assumes also to seek the judicial policy of the French Court of Cassation with regard to this case of appeals in cassation compared to the legislative developments and case law in Italy, which may see an erosion of the motivation’s control.Recently the art. 54, par. 1, l. b), d.l. n. 83/2012 has transformed the grounds for cassation «failure, insufficient or contradictory reasoning about a controversial and decisive fact for the judgment» (art. 360, par. 1, n. 5, Italian c.p.c.) in that of «failing to examine about one crucial fact for the judgment which has been the object of discussion between the parties», thus raising the question of the possibility to continue denouncing the defect of insufficient motivation to the Supreme Italian Court.In particular, the comparative study aims to analyse the way, the technique and the objectives with which the French Court of cassation guarantees the parties against the arbitrary exercise of judicial power in order to identify, for a verse, an interpretative solution which will allow to continue to censor the use - or rather the failure to consider - the maximum of experience under the new art. 360, par. 1, n. 5, c.p.c. and, secondly, to identify the similarities and differences between the control of the French and Italian Highs Courts on the motivation of judgments.

The diploma thesis deals with the tax system of Sweden. The object of this thesis is to describe a tax system which differs from the other countries of the European Union. The bulk of this thesis is the analysis of the development of Swedish tax system in dependence on economic and political situation of the country, the introduction of actual tax conditions and current changes relating to the taxation originating in the economic development of the country, progressive European integration and also in the worldwide financial crisis. Furthermore, this work compares basic tax indicators within Sweden and other states of the European Union. On the basis of such a diploma thesis, the reader should acquire a complex insight into the character and specifics of the Swedish tax system.

This thesis should typify different real ways of tax basis interferences with the help of creative accounting. My thesis describes different examples uncovered by the tax office - reduction of revenues, rise of costs, acceleration of costs or relationships between related persons, that have an influence on tax basis. Components of my thesis are also the chapters on personal consumption of businessman, deficits, surpluses and mistakes.

En cinématique il n'existe aucune méthode permettant de générer les conditions d'assemblage sous forme symbolique pour les systèmes de solides, éventuellement surcontraints. En revanche il existe un grand nombre de formules permettant- en principe - de calculer la mobilité. Les noms de Kutzbach, Grübler et Tchebytcheff sont associés à différentes formules bien connues mais aucune formule infaillible n'a jamais été trouvée. C'est ce qui motive notre proposition de méthodes numériques et symboliques constructives. Celles-ci permettent de générer automatiquement les conditions d'assemblage et de mobilité à partir de la connaissance des équations de fermeture des boucles de solides. Les méthodes numérique et symbolique présentées dans cette thèse se basent sur un socle commun. Elles utilisent les paramètres de Denavit-Hartenberg et les classent en deux catégories: la première catégorie, notée u pour usinage, représente les dimensions géométriques des solides, la seconde, notée m pour mobilité, représente les paramètres de position relative de deux solides en contact. Ensuite, les équations de fermeture sont obtenues par une méthode ``coordinate free'' à partir d'une matrice de Gram. C'est à cette étape que les deux méthodes diffèrent. Dans le cas de l'analyse numérique locale, le système d'équations est linéarisé. La décomposition en valeur singulière est utilisée pour l'élimination des paramètres. Nous obtenons ensuite les conditions d'assemblage dans un voisinage de la configuration initiale. Les conditions de mobilité sont calculées à partir des conditions d'assemblage issues d'un nombre fini de configurations. Dans le cas de l'analyse symbolique, nous calculons formellement la base de Gröbner associée aux équations de fermeture et cela grâce à l'algorithme FGb de Faugère. Il existe peu de références sur l'utilisation des Bases de Gröbner en cinématique, et aucune ne présente une analyse exhaustive du problème. Avec l'ordre lexicographique, nous ne gardons que des paramètres u et éliminons tous les autres. Lorsque ces relations en u sont vérifiées, elles représentent les conditions d'assemblage, dites relations de surcontraintes. Cet ensemble peut être vide lorsque le système est isocontraint. Pour générer les conditions de mobilité, nous gardons tous les u et un paramètre de mobilité. En annulant les coefficients en facteur de ce paramètre de mobilité, un nouveau système qui ne dépend que de u est construit. Les conditions de mobilité sont obtenues en calculant la base de Gröbner du nouveau système. Pour atteindre les résultats désirés, nous avons également proposé deux outils: saturation et contrainte. Ils permettent de parcourir un sous-ensemble de solutions représentées par une base de Gröbner. La confrontation des résultats obtenus dans la thèse avec ceux de la littérature, pour quelques de mécanismes connus, permet d'affirmer la validité et la complétude de la méthode. / In mechanical kinematics analysis, no generic method allows to generate symbolic assembly conditions for mechanisms with rigid bodies (especially for overconstrained mechanisms). However, many formulas can help to compute mobility. Kutzbach, Grübler and Tchebitcheff are associated to different formulas but none of them works in every case. For this reason, we propose generic numerical and symbolic methods in order to obtain assembly and mobility conditions from closed-loop equations. The numerical and symbolic methods presented in this thesis have the same starting point. They both use Denavit-Hartenberg parameters. These parameters are divided into two types : the first is called u, representing geometric dimensions of rigid bodies ; the second type is called m (for parameters of mobility), representing the relative motion between two rigid bodies in contact. First of all, closed-loop equation are written using a coordinate free method based on Gram matrix. After this step, the two methods differ. In case of numerical analysis, the system of equations is linearized. The Singular Value Decomposition is used to eliminate parameters. We then compute assembly conditions in the neighborhood of the initial configuration. Mobility conditions are computed based on assembly conditions which result from a finite number of configurations. In case of symbolic analysis, we calculate the Gröbner basis associated with closed-loop equations in order to eliminate parameters of mobility. There are few references talking about the application of Gröbner basis in kinematics analysis. None of these references provides a well explained analysis of kinematics problem. Since we have been collaborating with Mr. Faugère, we use the package “FGb” for the elimination of parameters of mobility. With a specified order, relations between the u parameters could be computed by eliminating the m parameters. When verified, these relations are assembly conditions, also named over-constrained assembly conditions. This set of relations may be empty when the studied system is iso-constrained. To generate mobility conditions, one has to keep all u parameters and only one parameter of mobility. When mobility parameter’s coefficients vanish, the mechanism is mobile with 1 degree of freedom. To determine two kinds of conditions, we propose also two tools : saturation and constraint. They allow browsing a subset of system’s solutions which is represented by a Gröbner basis. Since our results are identical to the ones found in literature, our method is valid and complete.