El peronismo y la construcción de una nueva legitimidad política (1943-1955)

En esta ponencia se analizarán los propósitos generales y los primeros avances de una investigación que forma parte de un proyecto UBACyT, que se desarrolla bajo mi dirección. Su objetivo consiste en analizar el proceso de construcción de una nueva legitimidad política en tiempos del "peronismo clásico" (1943-1955), en el marco de la discusión sobre las prácticas políticas y las características del espacio público en Buenos Aires durante el período. En esta ponencia exploraré una de las hipótesis centrales de mi investigación, que sostiene que la nueva legitimidad del régimen político peronista parece haber sido el resultado de una tensión entre un sistema de legitimación característico del consenso liberal pre-existente, asentado sobre la combinación entre representación política (ejercida a través del sufragio) y consenso de la opinión pública, y un nuevo marco ideológico, inspirado en el basamento de algunos regímenes "populistas" y autoritarios de la época, fundamentalmente en lo referido a las prácticas plebiscitarias y la movilización vertical, organizada y manipulada de las masas obreras, que no desechó, sino que incluyó a su pesar, en un plano subordinado, al ejercicio del sufragio.Fil: Lettieri, Alberto R. Universidad de Buenos Aires; Argentina

The effect of temperature on the minimum fluidization conditions of industrial cohesive particles

In order to understand the factors responsible for changes in the fluidization behaviour of industrial particles at high temperatures, an experimental campaign was performed using a 140 × 1000 mm heated gas fluidized bed. Five powder cuts sieved out of the same mother powder covering Group B, A and C of Geldart's classification were investigated over a range of temperatures from ambient to 500 °C. The results show that the mean size distribution affects significantly the fluidization behaviour of the materials investigated. In particular, significant differences were observed in the fluidization behaviour of the coarsest samples (Group B-A) and finest samples (Group A-C). The minimum fluidization conditions were compared with the prediction of the Ergun equation. The comparison was satisfactory only when accounting for the experimental values of the bed voidage. In fact, the non-monotonic trend of the minim velocity for fluidization with increasing temperature cannot be explained only with the effects of temperature on the bed fluid dynamics. But several others are the observed effects on the fluidization behaviour due to the temperature rise that can be ascribed to the enhanced interparticle forces: 1) the increase of the peak of pressure drops, close to the minimum for fluidization, in the fluidization curve at increasing gas velocities; 2) the increase for the finest samples of the hysteresis in the fluidization curves, considering the fluidization and defluidization branches of the curve; 3) a greater tendency of the bed to expand homogeneously; 4) the increasing difference between the parameters of the Richardson-Zaki equation found with a fitting procedure on the experiments and those found using the Richardson-Zaki correlations and the theoretical terminal velocity. Furthermore, in the cases where larger interparticle forces were expected, the X-Ray facility allowed to identify different internal structures within the bed. Mostly vertical channels but also, in the case of the finest powder tested, horizontal channels

Detection and estimation of capillary interparticle forces in the material of a fluidized bed reactor at high temperature by powder flow characterization

Two ceramic powder samples having different compositions of surface impurities and particle size distributions were considered. These two samples resulted from a high temperature fluidized bed reactor which in its operation showed changes of working condition that might be attributed to the onset of strong interparticle forces. The flow behaviour of these powders was characterized by the High Temperature Annular Shear Cell (HT-ASC), between ambient temperature and 500 °C. Furthermore, a model is developed to relate the change of the powder flowability to the formation of a liquid phase due to the melting of particle impurities present on the particle surface. In particular, the model is used to predict, on the base of the salt composition, the intensity of the interparticle forces at different temperatures. The interparticle forces predicted by the model can be compared with those that can be inferred from the powder flow properties measured with the HT-ASC. Therefore, it is demonstrated that it is possible to derive a theoretical model to predict interparticle forces in a particulate material relevant to fluidized bed reactor, on the basis of the impurities composition. Furthermore, it is demonstrated the possibility to correctly estimate the intensity of average interparticle forces in the same kind of material by the interpretations of bulk flow properties measured with a shear tester, even in the case in which capillary forces take the place of the much weaker van der Walls forces. More in general, the paper suggests a method by which powder rheology can be used to indirectly evaluate the effects of the interparticle forces on fluidization processes even in case in which strong capillary interaction occur

Life cycle assessment of conventional and advanced two-stage energy-from-waste technologies for methane production

This study integrates the Life Cycle Assessment (LCA) of thermal and biological technologies for municipal solid waste management within the context of renewable resource use for methane production. Five different scenarios are analysed for the UK, the main focus being on advanced gasification-plasma technology for Bio Substitute natural gas (Bio-SNG) production, anaerobic digestion and incineration. Firstly, a waste management perspective has been taken and a functional unit of 1 kg of waste to be disposed was used; secondly, according to an energy production perspective a functional unit of 1 MJ of renewable methane produced was considered. The first perspective demonstrates that when the current energy mix is used in the analysis (i.e. strongly based on fossil resources), processes with higher electric efficiency determine lower global warming potential (GWP). However, as the electricity mix in the UK becomes less carbon intensive and the natural gas mix increases the carbon intensity, processes with higher Bio-SNG yield are shown to achieve a lower global warming impact within the next 20 years. When the perspective of energy production is taken, more efficient technologies for renewable methane production give a lower GWP for both current and future energy mix. All other LCA indicators are also analysed and the hot spot of the anaerobic digestion process is performed

Thermodynamic modelling and evaluation of a two-stage thermal process for waste gasification

Tar generation and ash disposal represent the strongest barrier for use of fluid bed gasification for waste treatment, whereas sufficing for both is only possible with expensive cleaning systems and further processing. The use of plasma within an advanced two-stage thermal process is able to achieve efficient cracking of the complex organics to the primary syngas constituents whilst limiting the electric power demand. This study focused on the thermodynamic assets of using a two-stage thermal process over the conventional single-stage approach. These include, for example, the fact that the primary thermal waste decomposition is performed in conditions of optimal stoichiometric ratio for the gasification reactants. Furthermore, staging the oxidant injection in two separate intakes significantly improves the efficiency of the system, reducing the plasma power consumption. A flexible model capable of providing reliable quantitative predictions of product yield and composition after the two-stage process has been developed. The method has a systematic structure that embraces atom conservation principles and equilibrium calculation routines, considering all the conversion stages that lead from the initial waste feed to final products. The model was also validated with experimental data from a demonstration plant. The study effectively demonstrated that the two-stage gasification system significantly improves the gas yield of the system and the carbon conversion efficiency, which are crucial in other single stage systems, whilst maintaining high energy performances

Selective laser sintering of ceramic powders with bimodal particle size distribution

This paper addresses the possibility of carrying out Selective laser sintering (SLS) using powders obtained as mixtures of particles of different size. The beam source used in the experiments was a CO2 laser tube with a nominal power of 40W. The materials used were model Glass beads and a real ceramic material characterized by irregular shape of the particles. Bimodal distributed powders were generated by mixing samples characterized by different narrow particle size distributions. Single layer sintered specimens were obtained with a laser scanning speed of 50 mm/s and 8W beam. The sintered specimens were studied by means of microphotography and were characterized in terms of bulk density and tensile strength.Results show that the strength of the sintered specimen is significantly dependent upon the amount of fines in the powder mixture, in spite of the limited effects on the specimen thickness and density. In particular, the highest strength of the sintered material are observed with the highest fraction of fines in the originating powder mixture. In order to estimate the value of the forces between particles of different size produced by the sintering action, the model developed by Liu et al. (2017), based on the Rumpf (1958) approach, was purposely adapted. The application of the model revealed that in our process conditions the connection between large and fines particles is significantly weaker than the force between particles of the same size. The model also indicates that the strength of the sintered materials from mixtures can potentially increase up to values significantly higher than those of the materials sintered starting from the unimodal powder components

Life-cycle Inventory data and impacts on electricity production at the United Downs Deep Geothermal Power project in the UK

This data article supports the research article “Geothermal energy in the UK: the life-cycle environmental impacts of electricity production from the United Downs Deep Geothermal Power project”. The article reports inventory data, primarily on the construction of the geothermal wells, that is not reported in the main article, and the complete, disaggregated numerical values of the life-cycle environmental impacts reported only in part and in graphical form in the research article. The article also includes data supporting comparative analyses between deep geothermal energy and other energy technologies in the UK, and between the impacts of the construction of wells in a deep and conventional power plant

Selective laser sintering of ceramic powders with bimodal particle size distribution

This paper addresses the possibility of carrying out Selective laser sintering (SLS) using powders obtained as mixtures of particles of different size. The beam source used in the experiments was a CO2 laser tube with a nominal power of 40 W. The materials used were model Glass beads and a real ceramic material characterized by irregular shape of the particles. Bimodal distributed powders were generated by mixing samples characterized by different narrow particle size distributions. Single layer sintered specimens were obtained with a laser scanning speed of 50 mm/s and 8 W beam. The sintered specimens were studied by means of microphotography and were characterized in terms of bulk density and tensile strength. Results show that the strength of the sintered specimen is significantly dependent upon the amount of fines in the powder mixture, in spite of the limited effects on the specimen thickness and density. In particular, the highest strength of the sintered material are observed with the highest fraction of fines in the originating powder mixture. In order to estimate the value of the forces between particles of different size produced by the sintering action, the model developed by Liu et al. (2017), based on the Rumpf (1958) approach, was purposely adapted. The application of the model revealed that in our process conditions the connection between large and fines particles is significantly weaker than the force between particles of the same size. The model also indicates that the strength of the sintered materials from mixtures can potentially increase up to values significantly higher than those of the materials sintered starting from the unimodal powder components