In September 1993, the United States Congress formally ratified the North American Free Trade Agreement (NAFTA) in conjunction with the legislatures of Canada and Mexico. NAFTA phases out tariff barriers between the United States, Canada, and Mexico over a period of several years. The primary purpose of this study is to provide an empirical tool for evaluating the effects of NAFTA on beef trade between Canada, Mexico, and the United States. Trends were identified in U.S. beef exports and imports to Canada and Mexico over a period of several years. From the data on import/export quantities and prices, relevant elasticities were estimated for the the three trading partners using a partial adjustment modeling technique. Given the elasticities, relevant statistical tests were performed to determine the significance of price and quantity changes. This was done to determine whether changes in trading practices were consistent. Finally, policy recommendations were developed based on the assessment of NAFTA on U.S. beef trade. An overall direction of trade among the three countries was determined. Policies and implications based on economic theory were developed.

The cut slopes at a segment between Km 25+600 and 26+000 of the Antalya-Burdur Breakaway-Korkuteli State Road to be newly constructed have slope instability problems due to the existence of highly jointed limestone. The purpose of this study is to investigate the engineering geological properties of the units exposed at three cut slopes, to assess stability of the cut slopes, and to recommend remedial measures for the problematic sections. In this respect, both field and laboratory studies have been carried out. The limestone exposed at the cut slopes are beige to gray, fine grained, fossiliferous, and highly jointed. It has two joint sets and a bedding plane as main discontinuities. The kinematic analysis indicates that planar failure is expected at Km: 25+900. Limit equilibrium analysis show that the cut slopes with bench have no slope instability problems except rockfalls which endanger the traffic safety. In this thesis it is recommended to covering the cut slope with wire mesh and fibre reinforced shotcrete

Recent tailings dam failures around the world have highlighted the real risk posed by undrained slope failures. Undrained failures are fundamentally different to drained failures in the sense that different mechanisms are involved (i.e. a slope may be stable against drained failure but unstable against undrained failure). Popular methods to assess the stability of slopes against undrained failure involve the use of limit equilibrium analyses with both drained and undrained strengths assigned in the same analysis. A potential shortcoming of these methods is that no consideration is given to strain compatibility. In this study, a limit equilibrium based method where strain compatibility is maintained on the failure surface was developed. The method, referred to as the strain mobilisation method, considers a Mohr circle of stress at failure to determine the shear strength mobilised on the failure plane for use in the stability analysis as a function of the deviator stress imposed on the triaxial test result. The mobilisation of stress on a failure plane with strain was determined based on the stress-strain relationships observed during triaxial tests. A Factor of Safety (FoS) was used to express the stability of the slope as a function of the mobilised strain and the calculated FoS results obtained using the proposed method were compared to calculated FoS results using traditional methods. This was done for three tailings materials (gold, iron and platinum) for three specific hypothetical slopes. As an additional check, the proposed method was tested on Nerlerk sand, a well-known sand showing strain-softening behaviour during undrained shearing. It was found that, in general, as mobilised strain is increased, the FoS calculated using the proposed method converges to that of traditional methods so that there was no significant difference in calculated FoS between the current methods and the proposed method that does consider strain compatibility. This indicates that the proposed method provides FoS values comparable to those calculated using currently accepted methods where the failure surface passes predominantly through a single material type. For such a case, there does not appear to be a need to consider limit equilibrium methods where strain compatibility is maintained. The proposed method provides an indication of the amount of strain that may be expected to mobilise to provide the FoS. Given that this amount of strain is not excessive, the current methods which do not consider strain compatibility perform satisfactorily and can continue to be used / Dissertation (MEng (Civil Engineering))--University of Pretoria, 2021. / Civil Engineering / MEng (Civil Engineering) / Unrestricted

The aim of this study is to analyse the impacts of the social security system reform performed in Turkey within the

Orientador: Átila Madureira Bueno / Resumo: O som é uma onda mecânica e como tal transporta energia que age sobre partículas devido às forças de radiação acústica. O princípio para suspender corpos é aplicar uma força de tal forma a equilibrar seu peso. Na técnica de levitação acústica (AcLev) uma pequena esfera pode ser suspensa pela força de radiação acústica gerada por uma onda estacionária, sendo que o ponto de levitação está localizado na região em que o potencial acústico é mínimo, que é condição necessária para levitar uma esfera com raio muito menor que o comprimento de onda. Levitação acústica (AcLev) é uma ferramenta importante para manusear objetos sem contêineres. Nos anos recentes muitos dispositivos foram desenvolvidos com sucesso devido ao comportamento estável dos dispositivos AcLev. Como resultado, a maioria dos trabalhos sobre Aclev se concentram sobre simulações numéricas ou testes experimentais para estudar a geometria e arranjos dos emissores acústicos, ou a influência de vários tipos de perturbações, e a maioria desses modelos matemáticos considera somente o potencial acústico. Neste trabalho, a equação não linear de movimento para uma partícula levitada imersa em campo acústico de eixo único foi desenvolvida, considerando também forças dissipativas. O espaço parâmetro foi examinado buscando a existência de bifurcações, e faixas de projeto para os ganhos do dispositivo AcLev foram determinadas a partir da condição de existência de pontos de equilíbrio. Em adição, o comportamento dinâmico do dispos... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Sound is a mechanical wave and aims to carry energy that acts on particles due to acoustic radiation forces, while the principle to suspend bodies is to apply a force in such a way as to balance their weight. In the acoustic levitation technique (Aclev) a small sphere can be suspended by the acoustic radiation force generated by a stationary wave and the levitation point is located in the region where the acoustic potential is minimal, which is a necessary condition for levitating a sphere with radius much smaller than the wavelength. AcLev is an important tool for handling objects without the use of containers. In recent years many devices have been successfully developed due to the stable behavior of AcLev. As a result, most works on Aclev focuses on numerical simulations and experimental tests to study the geometry and arrangement of acoustic emitters, or the influence of various kinds of perturbations, and most mathematical models consider only acoustic potential. In this work, the nonlinear equation of motion for a levitated particle immersed in an acoustic field with single axis was developed considering also dissipative forces. The parameter space was searched for the existence of bifurcations and the design range for AcLev device gains were determined from the condition of equilibrium points. In addition, the dynamic behavior of the AcLev device regarding gains has been studied, also considering the microgravity situation. Numerical simulations corroborated the analyt... (Complete abstract click electronic access below) / Mestre

The thesis is a summary and discussion of eight papers. During the last decades, precipitation has become increasingly acidic due to the extensive use of fossil fuels. In areas of poorly buffered bedrocks, e.g. Scandinavia, northeastern United States, this phenomenon has resulted in elevated amounts of Al(III) being leached into streams and lakes. Recent findings reveal that these elevated Al-concentrations could cause fish death and decreasing forest production. In the present thesis, the importance of taking naturally occurring substances into consideration when discussing Al(III) in natural waters, is emphasized. On the basis of a chemical characterization of relevant ligand classes in a natural water, the complex formation between Al^+, hydroxide ions and the inorganic ligand carbonic acid, the low-molecular weight organic ligand citric acid and the high-molecular weight model substances gallic acid, 1,2-dihydroxynaphtha-lene-4-sulfonate, 1,2-naphthoquinone-4-sulfonate, pyrocatechol and salicylic acid were investigated. The investigations were performed as series of Potentiometrie titrations and data were processed by means of the least-squares computer program LETAGROPVRID using a technique called pqr-analysis, permitting an unbiased search for complex model (and corresponding equilibrium constants) to be made. In most systems studied, the complexation at high ligand excesses can be described by a series of mononuclear complexes AIL-AIL^. Tentatively, the whole series consists of octahedrally coordinated (water and ligand oxygens) AI(III). At lower ligand excesses, the significance and in some cases even predominance of ternary mono- and polynuclear hydroxo complexes is demonstrated. In two of the systems, binary aluminium hydroxo species are evaluated. The potential importance of the substances with respect to Al-com-plexation in natural waters are indicated in a number of model calculations. The solubility of the clay mineral kaolinite is calculated as a function of -lg[H+] and ligand concentration. It is shown that citric acid, gallic acid, 1,2-dihydroxynaphthalene-4-sulfonate, pyrocatechol and salicylic acid contribute quite significant to the total solubilities, even at very low concentrations. As a complement and background to the equilibrium studies, the corrosion rate for one of the naturally occurring Al-bearing minerals, corundum, is reported. In this investigation, performed with a leach-ant solution of ground-water composition, an experimental technique was employed which made it possible to divide the corrosion into chemical and mechanical losses. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1983</p> / digitalisering@umu

<div>This thesis has three major chapters. Structural estimation of non-homothetic demands is the element that is the most common across the three papers in which structural parameters from the data.<br></div><div><br></div><div><b>First Chapter</b>: Preference structures in applied general equilibrium models are commonly in favor of the family of linear expenditure system (LES) due to the desire for global regularity and applicability, while other emerging preference functions include the constant-elasticity-of-substitution (CES) forms that are used as sub-utility functions to fulfil regularity conditions with additional flexibilities. Hanoch (1975) introduces indirect, implicit additive relationships—a generalization of the CES—to obtain more flexible demand relationships that are globally regular. These preference relationships unlink substitution effects from income effects in ways that go beyond relaxation of homotheticity, and are more flexible than their direct dual. However, the estimation of these models as demand systems has proven to be challenging, and most published work in this area has focused on estimation approaches that involve approximations or that cannot fully identify parameter values in the preference relationships. Essay one introduces a direct approach which avoids approximations and allows parameters to be identified. We demonstrate the estimation using the readily accessible Global Trade Analysis Project (GTAP) and the confidential World Bank (International Comparison Program) databases, estimating the constant difference of elasticity or CDE directly in a maximum likelihood framework. In doing this, we show that the global regularity conditions stated in Hanoch (1975) can be slightly relaxed, and that the relaxed parametric conditions facilitate estimation. We introduce a normalization scheme that is beneficial for the scaling of the parameter values and which appears to have little impact on the economic performance of the estimated system. We develop a numerical test that justifies the normalization scheme. The series of procedures developed in this paper applied to this empirical example is generalized to solve many other econometric problems of general demand models of the Bergson family and those that are under-identified using reduced-form approaches. </div><div><br></div><div><b>Second Chapter</b>: This paper presents a general equilibrium gravity model of trade based on the constant difference of elasticities of substitution preferences. Hanoch (1975) illustrates these preferences' advantages in terms of parsimony and flexibility. This paper introduces a parsimonious, non-homothetic and globally well-behaved demand model into the gravity model that both separates substitution effects from income effects and has non-constant substitution elasticities. These features of the demand model---together with the structural estimation procedure devised in this paper---allow nesting several prominent theoretical motivations for the gravity model, and exploring the merits of this more general model. They also allow identification of the elasticity of trade costs with respect to distance and asymmetric border coefficients from the elasticity of trade flows with respect to trade costs. Most previous studies cannot separately identify these structural parameters. </div><div><br></div><div><b>Third Chapter</b>: The primary advantage of structural approaches to estimating the gravity model of trade is that they allow a transparent mapping of regression coefficients to structural parameters. Unfortunately, as shown in essay two, existing structural estimation methods are unable to separately identify trade costs and the trade elasticity without incorporating external data. We demonstrate that theoretical structure is alone sufficient for identifying all of the structural parameters of the canonical constant elasticity of substitution (CES) gravity model. We accomplish this by adopting an implicitly indirect representation of utility and estimating structurally using a mathematical program with equilibrium constraints. Our estimate of the elasticity of substitution is much smaller than in much of the rest of the literature, an outcome that we attribute to Pigou's Law, which ties income and substitution elasticities together in demand systems that assume additive preferences. This restriction is undesirable in demand systems, generally, and is a critical weakness for the canonical gravity model, a model that is commonly used to interpret the geographic trade pattern and to infer the welfare gains from trade. We demonstrate a non-homothetic CES model that both achieves identification and relaxes this restriction. Our counterfactual results based on the model suggest that the combination of a lower elasticity and lower trade costs generate a larger welfare change due to border removal compared to the CES model.<br></div>

The annual budget cycle in urban road/transport authorities by implication requires transport infrastructure projects to be ranked in terms of their relative value, to enable project selection by starting from the most deserving proposal. This follows from the fact that the total cost of feasible projects practically always exceeds available funds, signalling the need for some kind of selection protocol. Cost benefit analysis (CBA), when applied in a narrow sense, is not suitable for this purpose as it focuses on economic efficiency only. Attempts to broaden it have been criticized by some scholars. Although the diversity of impacts points to a multi-criteria analysis (MCA) approach, this is considered unscientific in certain quarters; at best, its practical value needs to be demonstrated. In the case of the City of Tshwane (CoT), problems with current project appraisal are evident in that different methods – none of which is defensible – are used, sometimes resulting in rankings that are contradictory. This thesis therefore attempts the following: (a) to develop a basic approach that combines the best elements of traditional methods; (b) to customize this approach to the specific context and needs of road authorities in the municipal sphere of government, using CoT as an example; and (c) to demonstrate the application of the resulting appraisal framework, utilizing appropriate decision-support software for this purpose. Recommendations include the following: An appraisal framework should combine CBA and MCA by adopting an overall MCA approach with economic efficiency – focusing on the optimal allocation of scarce resources – as one of the decision criteria. For completeness‟ sake, three additional decision criteria are deemed necessary: equity (focusing on income distribution impacts); sustainability (focusing on environmental impacts); and compatibility (focusing on the alignment of projects with stated goals and objectives). This framework may well apply to road authorities in other spheres of government – the optimum application in each case will depend on the composition of the relevant decision-making team. The inherent nature of project appraisal requires a two-phased approach in all cases: the evaluation of mutually exclusive alternatives, followed by the ranking of independent projects. State-of-the-art decision support software is indispensable for implementing this framework. / Transport Economics / D. Com. (Transport Economics)

The annual budget cycle in urban road/transport authorities by implication requires transport infrastructure projects to be ranked in terms of their relative value, to enable project selection by starting from the most deserving proposal. This follows from the fact that the total cost of feasible projects practically always exceeds available funds, signalling the need for some kind of selection protocol. Cost benefit analysis (CBA), when applied in a narrow sense, is not suitable for this purpose as it focuses on economic efficiency only. Attempts to broaden it have been criticized by some scholars. Although the diversity of impacts points to a multi-criteria analysis (MCA) approach, this is considered unscientific in certain quarters; at best, its practical value needs to be demonstrated. In the case of the City of Tshwane (CoT), problems with current project appraisal are evident in that different methods – none of which is defensible – are used, sometimes resulting in rankings that are contradictory. This thesis therefore attempts the following: (a) to develop a basic approach that combines the best elements of traditional methods; (b) to customize this approach to the specific context and needs of road authorities in the municipal sphere of government, using CoT as an example; and (c) to demonstrate the application of the resulting appraisal framework, utilizing appropriate decision-support software for this purpose. Recommendations include the following: An appraisal framework should combine CBA and MCA by adopting an overall MCA approach with economic efficiency – focusing on the optimal allocation of scarce resources – as one of the decision criteria. For completeness‟ sake, three additional decision criteria are deemed necessary: equity (focusing on income distribution impacts); sustainability (focusing on environmental impacts); and compatibility (focusing on the alignment of projects with stated goals and objectives). This framework may well apply to road authorities in other spheres of government – the optimum application in each case will depend on the composition of the relevant decision-making team. The inherent nature of project appraisal requires a two-phased approach in all cases: the evaluation of mutually exclusive alternatives, followed by the ranking of independent projects. State-of-the-art decision support software is indispensable for implementing this framework. / Transport Economics / D. Com. (Transport Economics)

Στην παρούσα διατριβή μελετάμε αγορές δημοπρασιών και εξετάζουμε διάφορες ιδιότητές τους καθώς και τον τρόπο που αυτές επηρεάζονται από τον τρόπο που συμπεριφέρονται και δρουν οι συμμετέχοντες. Η έννοια δημοπρασία αναφέρεται σε κάθε μηχανισμό, ή σύνολο κανόνων, που διέπει μια διαδικασία ανάθεσης αγαθών. Τέτοιοι μηχανισμοί είναι επιρρεπείς σε στρατηγικούς χειρισμούς (χειραγώγηση) από τους συμμετέχοντες, γεγονός που δικαιολογεί την έμφυτη δυσκολία στον σχεδιασμό τους. Σκοπός αυτής της εργασίας είναι η μελέτη σε θεωρητικό επίπεδο των ιδιοτήτων μηχανισμών δημοπρασίας έτσι ώστε να είμαστε σε θέση να προβλέψουμε, να εξηγήσουμε, ακόμα και να τροποποιήσουμε την απόδοσή τους στην πράξη. Εστιάζουμε την προσοχή μας σε δημοπρασίες χρηματοδοτούμενης αναζήτησης, οι οποίες αποτελούν την επικρατέστερη διαδικασία για την προβολή διαφημίσεων στο Διαδίκτυο. Υιοθετούμε παιγνιοθεωρητική προσέγγιση και υπολογίζουμε το Τίμημα της Αναρχίας για να φράξουμε την απώλεια αποδοτικότητας εξαιτίας της στρατηγικής συμπεριφοράς των παιχτών. Επίσης, αποδεικνύουμε εγγυήσεις εσόδων για να φράξουμε την απώλεια των εσόδων του μηχανισμού δημοπρασίας GSP (γενικευμένος μηχανισμός δεύτερης τιμής) σε αυτό το πλαίσιο. Για την ακρίβεια, ορίζουμε παραλλαγές του μηχανισμού δημοπρασίας GSP που δίνουν καλές εγγυήσεις εσόδων. Στη συνέχεια εξετάζουμε το πρόβλημα του σχεδιασμού της βέλτιστης δημοπρασίας ενός αντικειμένου. Αποδεικνύουμε ένα υπολογίσιμο φράγμα δυσκολίας στην προσέγγιση για την περίπτωση με τρεις παίχτες. Επίσης, αποδεικνύουμε ότι υπάρχει αξιοσημείωτη διαφορά ανάμεσα στα έσοδα που προκύπτουν από ντετερμινιστικούς φιλαλήθεις μηχανισμούς και πιθανοτικούς μηχανισμούς που είναι φιλαλήθεις κατά μέσο όρο. / In this dissertation we consider auction markets and examine their properties and how these are affected by the way the participants act. An auction may refer to any mechanism or set of rules governing a resource allocation process. Designing such a mechanism is not an easy task and this is partly due to their vulnerability to strategic manipulation by the participants. Our goal is to examine the theoretical properties of auction mechanisms in order to predict, explain, or even adjust their behavior in practice in terms of some desired features. We focus on sponsored search auctions, which constitute the leading procedure in Internet advertising. We adopt a game-theoretic approach and provide Price of Anarchy bounds in order to measure the efficiency loss due to the strategic behavior of the players. Moreover, we prove revenue guarantees to bound the suboptimality of GSP (generalized second price mechanism) in that respect. Ιn particular, we define variants of the GSP auction mechanism that yield good revenue guarantees. We also consider the problem of designing an optimal auction in the single-item setting. We prove a strong APX-hardness result that applies to the 3-player case. We furthermore give a separation result between the revenue of deterministic and randomized optimal auctions.