Tariff-Rate Quotas, Rent-Shifting and the Selling of Domestic Access

Tariff-rate quotas (TRQs) have replaced quotas at the end of the Uruguay Round. We analyze TRQs when a foreign firm competes against a domestic firm in the latter’s market. Our benchmark is the strategic rent-shifting tariff. We show that the domestic price-equivalent TRQ is a better instrument welfare-wise, as it can extract all of the rents from the foreign firm. We show that different pairs of within-quota tariff and quota can support full rent extraction. The implication is that reduction of the former and enlargement of the latter, holding the above-quota tariff constant, may have no liberalizing effects. The first-best TRQ and the strategic tariff generate different prices. When firms have identical and constant marginal cost, the first-best TRQ entails selling a subsidy to the foreign firm and forcing the exit of the domestic firm.Financial Economics, International Relations/Trade, Marketing, Political Economy,

Développement de techniques numériques pour l'estimation, la modélisation et la prédiction de propriétés thermodynamiques et structurales de systèmes métalliques à fort ordonnancement chimique

Dans ce travail, la possibilité de calculer et d’évaluer avec précision l’énergie de Gibbs d’équilibres de phases complexes, pour lesquels le comportement énergétique des solutions solides métalliques est décrit par des modèles thermodynamiques décrivant simultanément les ordonnancements chimiques à courte et longue distance ainsi que des solutions métalliques liquides décrites par un modèle décrivant l’ordonnancement à courte distance, a été étudiée. Pour ce faire, les modèles thermodynamiques appelés « cluster site approximation » (CSA) et « cluster variation method » (CVM) ont été implémentés à l’intérieur d’une toute nouvelle technique de minimisation de l’énergie libre de Gibbs de systèmes multicomposants et multiphasiques pour décrire le comportement thermodynamique de solutions solides métalliques présentant un fort ordonnancement chimique. Le modèle quasichimique modifié avec approximation de paires (MQMPA) a également été implémenté dans le nouvel algorithme de minimisation pour décrire le comportement thermodynamique des solutions liquides. Ce nouvel algorithme de minimisation sous contraintes a été construit selon une approche de programmation quadratique séquentielle de type Newton exacte (c’est-à-dire l’usage de dérivées secondes exactes pour évaluer la matrice Hessienne de la fonction objective) avec recherche linéaire de direction de descente suffisante. L’implémentation de cette nouvelle technique de minimisation d’énergie de Gibbs sous contraintes a été nécessaire suite à la rencontre de difficultés quant à l’identification de l’état d’équilibre pour des conditions données lors de l’utilisation du logiciel FactSage lorsque les modèles mentionnés ci-haut sont simultanément présents pour décrire le comportement thermodynamique des phases présentes à l’équilibre (ex. : Solide_CSA+Liquide_MQMPA, Solide1_CSA+Solide2_CSA). Une fois le développement de la technique de minimisation de l’énergie de Gibbs validé pour plusieurs systèmes binaires et ternaires trouvés dans la littérature, il a été possible de paramétrer ces modèles de solutions solides pour des systèmes d’intérêt industriel tel les systèmes Cu-Zr et Al-Zr à partir de données thermodynamiques cohérentes générées à partir d’un simulateur Monte Carlo, complètement bâti dans le cadre de ce travail, utilisant le potentiel interatomique appelé « modified embedded atom model in the second nearest neighbour pair formalism » (MEAM-2NN) pour décrire l’énergie interne des structures étudiées. Ce potentiel interatomique a dû être paramétré pour les interactions mixtes du système Al-Zr dans le cadre de ce travail. Le chemin d’intégration thermodynamique a aussi été implémenté dans ce simulateur de façon à pouvoir évaluer l’énergie de Gibbs absolue des structures considérées tant solides que liquides, ce qui permet de déduire l’entropie. L’implémentation de cette technique a alors permis pour la première fois de calculer de manière théorique toutes les contributions de mélange (contributions enthalpiques et entropiques) d’une phase binaire liquide (Cu-Zr et Al-Zr) et solide (solution CFC Al-Zr) à partir du potentiel MEAM-2NN. Les propriétés thermodynamiques et structurales obtenues suite à de nombreuses simulations Monte Carlo couplées à des simulations de dynamique moléculaire classique ont ensuite été utilisées pour paramétrer les modèles thermodynamiques mentionnés précédemment pour la phase liquide du système Cu-Zr ainsi que la phase liquide et la solution solide cubique à faces centrées pour le système Al-Zr. L’étude de ces systèmes a également permis d’introduire de nouveaux paramètres d’excès fonction de la configuration de la solution solide décrite par les modèles CVM ou CSA pour améliorer la précision de ces modèles basé sur des évidences expérimentales trouvées dans la littérature. Un meilleur paramétrage du modèle quasichimique modifié pour la phase métallique liquide a également été proposé en tenant compte des fractions de paires calculées par simulations Monte Carlo et des différents effets de relaxation volumique indépendants de la configuration modélisés à partir de paramètres réguliers. Suite à la génération de données thermodynamiques cohérentes et au paramétrage subséquent des phases solides et liquide du système Al-Zr, un diagramme de phases respectant complètement ces données cohérentes dans l’intervalle de composition a été présenté. Des simulations Monte Carlo ont également été faites pour comprendre et définir le comportement thermodynamique de la phase amorphe du système Al-Zr. Finalement, les modèles thermodynamiques ainsi paramétrés pour les solutions solides, liquides et amorphes ont pu servir à définir les conditions, selon des critères thermodynamiques et volumétriques permettant de définir une gamme de composition, où les verres métalliques massifs peuvent être produits. ---------- In this work, the possibility to calculate and evaluate with a high degree of precision the Gibbs energy of complex multiphase equilibria for which chemical ordering is explicitly and simultaneously considered in the thermodynamic description of solid (short range order and long range order) and liquid (short range order) metallic phases is studied. The cluster site approximation (CSA) and the cluster variation method (CVM) are implemented in a new minimization technique of the Gibbs energy of multicomponent and multiphase systems to describe the thermodynamic behaviour of metallic solid solutions showing strong chemical ordering. The modified quasichemical model in the pair approximation (MQMPA) is also implemented in the new minimization algorithm presented in this work to describe the thermodynamic behaviour of metallic liquid solutions. The constrained minimization technique implemented in this work consists of a sequential quadratic programming technique based on an exact Newton’s method (i.e. the use of exact second derivatives in the determination of the Hessian of the objective function) combined to a line search method to identify a direction of sufficient decrease of the merit function. The implementation of a new algorithm to perform the constrained minimization of the Gibbs energy is justified by the difficulty to identify, in specific cases, the correct multiphase assemblage of a system where the thermodynamic behaviour of the equilibrium phases is described by one of the previously quoted models using the FactSage software (ex.: solid_CSA+liquid_MQMPA; solid1_CSA+solid2_CSA). After a rigorous validation of the constrained Gibbs energy minimization algorithm using several assessed binary and ternary systems found in the literature, the CVM and the CSA models used to describe the energetic behaviour of metallic solid solutions present in systems with key industrial applications such as the Cu-Zr and the Al-Zr systems are parameterized using fully consistent thermodynamic an structural data generated from a Monte Carlo (MC) simulator also implemented in the framework of this project. In this MC simulator, the modified embedded atom model in the second nearest neighbour formalism (MEAM-2NN) is used to describe the cohesive energy of each studied structure. A new Al-Zr MEAM-2NN interatomic potential needed to evaluate the cohesive energy of the condensed phases of this system is presented in this work. The thermodynamic integration (TI) method implemented in the MC simulator allows the evaluation of the absolute Gibbs energy of the considered solid or liquid structures. The original implementation of the TI method allowed us to evaluate theoretically for the first time all the thermodynamic mixing contributions (i.e., mixing enthalpy and mixing entropy contributions) of a metallic liquid (Cu-Zr and Al-Zr) and of a solid solution (face-centered cubic (FCC) Al-Zr solid solution) described by the MEAM-2NN. Thermodynamic and structural data obtained from MC and molecular dynamic simulations are then used to parameterize the CVM for the Al-Zr FCC solid solution and the MQMPA for the Al-Zr and the Cu-Zr liquid phase respectively. The extended thermodynamic study of these systems allow the introduction of a new type of configuration-dependent excess parameters in the definition of the thermodynamic function of solid solutions described by the CVM or the CSA. These parameters greatly improve the precision of these thermodynamic models based on experimental evidences found in the literature. A new parameterization approach of the MQMPA model of metallic liquid solutions is presented throughout this work. In this new approach, calculated pair fractions obtained from MC/MD simulations are taken into account as well as configuration-independent volumetric relaxation effects (regular like excess parameters) in order to parameterize precisely the Gibbs energy function of metallic melts. The generation of a complete set of fully consistent thermodynamic, physical and structural data for solid, liquid, and stoichiometric compounds and the subsequent parameterization of their respective thermodynamic model lead to the first description of the complete Al-Zr phase diagram in the range of composition based on theoretical and fully consistent thermodynamic properties. MC and MD simulations are performed for the Al-Zr system to define for the first time the precise thermodynamic behaviour of the amorphous phase for its entire range of composition. Finally, all the thermodynamic models for the liquid phase, the FCC solid solution and the amorphous phase are used to define conditions based on thermodynamic and volumetric considerations that favor the amorphization of Al-Zr alloys

Tariff-Rate Quotas, Rent-Shifting and the Selling of Domestic Access

Tariff-rate quotas (TRQs) have replaced quotas at the end of the Uruguay Round. We analyze TRQs when a foreign firm competes against a domestic firm in the latter\u27s market. Our benchmark is the strategic rent-shifting tariff. We show that the domestic price-equivalent TRQ is a better instrument welfare-wise, as it can extract all of the rents from the foreign firm. We show that different pairs of within-quota tariff and quota can support full rent extraction. The implication is that reduction of the former and enlargement of the latter, holding the above-quota tariff constant, may have no liberalizing effects. The first-best TRQ and the strategic tariff generate different prices. When firms have identical and constant marginal cost, the first-best TRQ entails selling a subsidy to the foreign firm and forcing the exit of the domestic firm

Phase transitions in the α–γ–β spodumene thermodynamic system and impact of γ-spodumene on the efficiency of lithium extraction by acid leaching

ABSTRACT: Heat-treatment of spodumene concentrate at 1323 K (1050 °C) for 30 min in a rotary kiln yielded a successful decrepitation. Particle size decreased from 2 cm to less than 425 µm for 80% of the initial mass. X-ray analysis of both fractions did not reveal the presence of α-spodumene or γ-spodumene. The coarse fraction was ground to less than 425 µm with minimal mechanical energy and mixed with the finer fraction to perform lithium extraction. The lithium extraction efficiency reached 98 wt% without the need for flotation. Some aspects of the thermodynamic behavior of the spodumene system were assessed. Results show that metastable γ-spodumene may hinder the formation of β-spodumene at lower heat treatment temperatures. Some heat-treated samples presented non-negligible γ-spodumene content and lithium extraction efficiency decreases as the γ content increases. Finally, the assumed irreversibility of the transformations was studied by analyzing heat-treated samples following long controlled-storage periods. The results show that concentrate composition is not static over the studied time. This suggests that the β formation is not as irreversible as claimed. It is recommended to avoid long periods between heat-treatment and extraction to avoid the slow conversion of β-spodumene to other allotropes, which are less susceptible to lithium extraction

Synthesis and characterization of (Al,Si)₃(Zr,Ti)-D0₂₂/D0₂₃ intermetallics: Understanding the stability of silicon substitution

ABSTRACT: (Al,Si)₃(Zr,Ti)-D0₂₂/D0₂₃ are phases that may form in aerospace and automotive aluminium alloys. The substitution of Zr/Ti in these solid solutions is widely reported in the literature; however, it remains relatively unexplored for Si. In this work, in situ precipitation of (Al,Si)₃(Zr,Ti)-D0₂₂/D0₂₃ intermetallics was performed using Al-Si-Zr-Ti alloys. The precipitation, sedimentation and concentration of numerous intermetallic particles were accomplished by filtrating the residual molten aluminium using a temperature/pressure-controlled vessel adapted with a PoDFA filter. A combination of SEM, TEM, XRD and EMP analysis allowed the identification of (Al,Si)₃(Zr,Ti)-D0₂₂/D0₂₃ intermetallics concentrated within α-FCC matrices of non-Si-doped (sample S2) and Si-doped (samples S4 and S6) alloys. EDS analysis confirmed that Zr and Ti substitute each other in the D0₂₂ and D0₂₃ phases, whereas Si substitutes in Al sites. Acceptance of Si inside the D0₂₃ phase was not expected according to FTlite (FactSage) and TCAL7 (Thermo-Calc) databases. Additionally, Si was found to enhance the formation of (Al,Si)₃(Zr,Ti)-D0₂₂ intermetallics with high Zr-content, contrary to FactSage 7.3 predictions. TEM results showed intermetallic/FCC crystal coherency for samples S2 and S6, implying that these intermetallics acted as nucleation sites for the Al-phase due to their small lattice mismatch. Furthermore, Si site occupancy was calculated for both (Al,Si)Ti-D0₂₂ and (Al,Si)₃Zr-D0₂₃ phases via DFT, showing that sites 2b and 4e are the most favorable for Si occupation, respectively. Finally, a thermodynamic model is derived to describe Si substitution upon solidification. Experimental and numerical examinations indicate that Si substitution preferentially occurs in the D0₂₂ intermetallics compared to the D0₂₃ phase

Quantification of the chemical reactivity of molten nitrate salts with heat treatable aluminum alloys

This work explores the conditions for safe heat treatment of aluminum alloys containing lithium and magnesium in molten sodium nitrate (NaNO3) bath furnaces, and conditions where industrial accidents may occur. Using calorimetry coupled to classical thermodynamics, the strength of classical thermodynamics when analyzing thermal curves was demonstrated through a series of small-scale thermal analyses of various aluminum alloys in contact with sodium nitrate. This system was selected to illustrate reactions that may lead to severe and violent heat effect phenomena. Using idealized binary alloys, severe oxidation of magnesium- and lithium-rich aluminum alloy samples were shown to occur near 500 °C, a temperature range dangerously close to the operating temperature of solution heat treatment furnaces in manufacturing processes of heat treatable aluminum alloy sheets used in the aerospace industry. Commercial aluminum alloys AW257, 2198, 2024, and 1050 were also assessed with the same tools. The temperature that needed to be reached for these commercial aluminum alloys to react with molten sodium nitrate was significantly higher than the normal operating temperature of a conventional solution heat treatment furnace

On the application of the factsage thermochemical software and databases in materials science and pyrometallurgy

ABSTRACT: The discovery of new metallic materials is of prime importance for the development of new technologies in many fields such as electronics, aerial and ground transportation as well as construction. These materials require metals which are obtained from various pyrometallurgical processes. Moreover, these materials need to be synthesized under extreme conditions of temperature where liquid solutions are produced and need to be contained. The design and optimization of all these pyrometallurgical processes is a key factor in this development. We present several examples in which computational thermochemistry is used to simulate complex pyrometallurgical processes including the Hall–Heroult process (Al production), the PTVI process (Ni production), and the steel deoxidation from an overall mass balance and energy balance perspective. We also show how computational thermochemistry can assist in the material selection in these extreme operation conditions to select refractory materials in contact with metallic melts. The FactSage thermochemical software and its specialized databases are used to perform these simulations which are proven here to match available data found in the literature

Novel formulations of oral bisphosphonates in the treatment of osteoporosis.

Oral bisphosphonates are a key intervention in the treatment of osteoporosis and in reducing the risk of fragility fractures. Their use is supported by over 3 decades of evidence; however, patient adherence to oral bisphosphonates remains poor in part due to complex dosing instructions and adverse events, including upper gastrointestinal symptoms. This problem has led to the development of novel oral bisphosphonate formulations. Buffered, effervescent alendronate is dissolved in water and so seeks to reduce upper gastro-intestinal adverse events, and gastro-resistant risedronate aims to reduce the complexity of dosing procedure (e.g. fasting prior to consumption) whilst still maintaining the efficacy of fracture risk reduction. Clinical trials and real-world data have been employed to demonstrate some benefits in terms of reduced upper gastro-intestinal adverse events, adherence, persistence and health economic outcomes. This report describes the result of an ESCEO (European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis) expert working group, which explores where oral bisphosphonates sit in current clinical practice guidelines, review their risk-benefit profile and the consequences of poor adherence before exploring novel oral bisphosphonate formulations and their potential clinical and health economic impact. Further research is required but there are signs that these novel, oral bisphosphonate formulations may lead to improved tolerance of oral bisphosphonates and thus, improved adherence and fracture outcomes

Role of vitamin D supplementation in the management of musculoskeletal diseases: update from an European Society of Clinical and Economical Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) working group.

Vitamin D is a key component for optimal growth and for calcium-phosphate homeostasis. Skin photosynthesis is the main source of vitamin D. Limited sun exposure and insufficient dietary vitamin D supply justify vitamin D supplementation in certain age groups. In older adults, recommended doses for vitamin D supplementation vary between 200 and 2000 IU/day, to achieve a goal of circulating 25-hydroxyvitamin D (calcifediol) of at least 50 nmol/L. The target level depends on the population being supplemented, the assessed system, and the outcome. Several recent large randomized trials with oral vitamin D regimens varying between 2000 and 100,000 IU/month and mostly conducted in vitamin D-replete and healthy individuals have failed to detect any efficacy of these approaches for the prevention of fracture and falls. Considering the well-recognized major musculoskeletal disorders associated with severe vitamin D deficiency and taking into account a possible biphasic effects of vitamin D on fracture and fall risks, an European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) working group convened, carefully reviewed, and analyzed the meta-analyses of randomized controlled trials on the effects of vitamin D on fracture risk, falls or osteoarthritis, and came to the conclusion that 1000 IU daily should be recommended in patients at increased risk of vitamin D deficiency. The group also addressed the identification of patients possibly benefitting from a vitamin D loading dose to achieve early 25-hydroxyvitamin D therapeutic level or from calcifediol administration