98 research outputs found
El Distrito Norte de la Baja California en disputa. Historias. Revista de la Dirección de Estudios Históricos. Num. 100 (2018) mayo-agosto
No full text1 Por ejemplo, Javier Garciadiego, “Esteban Cantú y la revolución constitucionalista en el Distrito Norte de la Baja California”, tesis de maestría en historia de América Latina, Universidad de Chicago, 1979; Max Calvillo, “Esteban Cantú en Baja California. Consideraciones en torno a su gobierno”, Yubai. Revista del Área de Humanidades, núm. 7, julio-septiembre, 1994, pp. 4-10, también Max Calvillo, “Indicios para descifrar la trayectoria política de Esteban Cantú”, Historia Mexicana, vol. 59, núm. 3 (235), enero-marzo, 2010, pp. 981-1040.2 Antoine Prost, Doce lecciones sobre la historia, Madrid, Cátedra, 2001, p. 96.3 A partir del 1 de enero de 1888, el antiguo Partido Norte de Baja California recibió la categoría política de Distrito Norte. Esta jurisdicción tenía un municipio (Ensenada de Todos los Santos), capital del Distrito, donde residía el jefe político. El coronel Esteban Cantú cambió la capital a Mexicali en 1915.4 César Alexis Marcial Campos, Un territorio en disputa. El Distrito Norte de la Baja California durante el gobierno de Esteban Cantú, 1915-1920, México, Gobierno del Estado de Baja California Sur / Conaculta / Instituto Sudcaliforniano de Cultura / Archivo Histórico Pablo L. Martínez, 2016, p. 12.5 Idem.6 Luis González y González, El oficio de historiar, México, Clío, 1995, p. 127 (Obras completas de Luis González y González, I).César Alexis Marcial Campos, Un territorio en disputa. El Distrito Norte de la Baja California durante el gobierno de Esteban Cantú, 1915-1920, México, Gobierno del Estado de Baja California Sur / Conaculta / Instituto Sudcaliforniano de Cultura / Archivo Histórico Pablo L. Martínez, 2016, 133 pp
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Estimation of aqueous solubility of organic compounds.
No full textThe relationship between aqueous activity coefficients (log γ(w)) and different physico-chemical properties has been studied for a number of solutes by both empirical correlations as well as by applying existing theoretical models. The solute properties selected have been classified into three categories: geometrical, polar, and electrostatic. The solutes chosen were divided into two major groups: (a) Training Set. Structurally simple compounds, i.e., each containing only one functional group, and (b) Test Set. A series of drugs and pollutants covering a wide variety of functional groups. The Training Set is in turn formed by four sub-sets of structurally related solutes, each representative of typical data sets used in the literature for solubility studies. Linear relationships were found for polar and geometric parameters in agreement with those reported in the literature. However, although the overall correlations are good, the quality of the regressions among the sub-sets is not uniform. The generality of the relationships obtained with the Training Set was tested by applying the obtained expressions to estimate log γ(w) of the solutes of the Test Set. It was found that the parameters of the theoretical models are the only ones whose relationship with log γ(w) is maintained for both the Training and the Test sets. The theoretical models used are: octanol-water partition coefficient estimated by both Rekker's (parameter LOGP) and by Leo's (parameter PCLOGP) methods; the solubility group contributions method of Wakita et al. (1986) (parameter WAKITA); the Linear Solvation Energy Relationships model (parameter KAMLET), and the UNIFAC model. The theoretical approaches were evaluated based on two criteria: accuracy of predictions and range of applicability. The accuracy of predictions was quantitated by a prediction coefficient, P², which although analogous to regression coefficient (R²) is far less flexible. Prediction coefficient is sensitive not only to scatter of the predictions but also to the systematic errors of the model being tested. The range of applicability was quantitated by the fraction (f) of solutes within the data set for which estimates by the given methodology are possible. The Accuracy-Generality Product (AGP) defined as the product of P² and f was used as the overall criterion for evaluation. The results indicated that the quality of predictions of the theoretical models as determined by the AGP is PCLOGP > LOGP > WAKITA > UNIFAC > KAMLET, for both the Training and Test sets
Analysis of microstructure and strengthening in CuMg alloys deformed by equal channel angular pressing
No full textThe microstructural and strengthening behavior of two CuMg alloys, with 0.2 and 0.5 m.-% of Mg, were analyzed after severe plastic deformation by Equal Channel Angular Pressing (ECAP). Both alloys were passed through a 90° inner angle ECAP die at room temperature up to 16 passes following route Bc. The EBSD analysis of the deformed microstructure revealed a significant grain refinement after the 2nd pass. Average grain sizes as fine as 0.31 and 0.24 µm for the CuMg0.2 and CuMg0.5, respectively, were obtained after 16 passes. The tensile strength of the ECAPed samples of the present CuMg alloys did not reach a saturation level, attaining 570 and 750 MPa after 16 passes for the CuMg0.2 and CuMg0.5, respectively. The dependence of the yield stress on deformation (i.e. number of ECAP passes) and Mg content was evaluated in terms of the Hall–Petch effect (influence of grain size), dislocation density (through the subgrain hardening effect) and solid solution strengthening. Results indicated that the stronger effect comes from the subgrain microstructure rather than from High Angle Grain Boundaries (HAGB). A minor effect of the chemical composition was also noticed.Postprint (author’s final draft
Analysis of microstructure and strengthening in CuMg alloys deformed by equal channel angular pressing
No full textThe microstructural and strengthening behavior of two CuMg alloys, with 0.2 and 0.5 m.-% of Mg, were analyzed after severe plastic deformation by Equal Channel Angular Pressing (ECAP). Both alloys were passed through a 90° inner angle ECAP die at room temperature up to 16 passes following route Bc. The EBSD analysis of the deformed microstructure revealed a significant grain refinement after the 2nd pass. Average grain sizes as fine as 0.31 and 0.24 µm for the CuMg0.2 and CuMg0.5, respectively, were obtained after 16 passes. The tensile strength of the ECAPed samples of the present CuMg alloys did not reach a saturation level, attaining 570 and 750 MPa after 16 passes for the CuMg0.2 and CuMg0.5, respectively. The dependence of the yield stress on deformation (i.e. number of ECAP passes) and Mg content was evaluated in terms of the Hall–Petch effect (influence of grain size), dislocation density (through the subgrain hardening effect) and solid solution strengthening. Results indicated that the stronger effect comes from the subgrain microstructure rather than from High Angle Grain Boundaries (HAGB). A minor effect of the chemical composition was also noticed
Energy Management in Smart Cities
No full textModels and simulators have been widely used in urban contexts for many decades. The drawback of most current models is that they are normally designed for specific objectives, so the elements considered are limited and they do not take into account the potential synergies between related systems. The necessity of a framework to model complex smart city systems with a comprehensive smart city model has been remarked by many authors. Therefore, this PhD thesis presents: i) a general conceptual framework for the modelling of energy related activities in smart cities, based on determining the spheres of influence and intervention areas within the city, and on identifying agents and potential synergies among systems, and ii) the development of a holistic energy model of a smart city for the assessment of different courses of action, given its geo-location, regulatory and technical constraints, and current energy markets. This involves the creation of an optimization model that permits the optimal planning and operation of energy resources within the city. In addition, several analyses were carried out to explore different hypothesis for the smart city energy model, including: a) an assessment of the importance of including network thermal constraints in the planning and operation of DER systems at a low voltage distribution level, b) an analysis of aggregator’s market modelling approaches and the impact on prices due to DER aggregation levels, and c) an analysis of synergies between different systems in a smart city context. Some of the main findings are: It is sensible to not consider network thermal constraints in the planning of DER systems. Results showed that the benefit decrement of considering network constraints was approximatively equivalent to the cost of reinforcing the network when necessary after planning without considering network constraints. The level of aggregation affects the planning and overall benefits of DER systems. Also, price-maker approaches could be more appropriate for the planning and operation of energy resources for medium to large aggregation sizes, but could be unnecessary for small sizes, with low expected impact on the market price. Synergies between different energy systems exist in an interconnected smart city context. Results showed that the overall benefits of a joint management of systems were greater than those of the independently managed systems. Lastly, the smart city energy model was applied to a case study simulating a real smart city implementation, considering five real districts in the southern area of Madrid, Spain. This analysis allowed to assess the potential benefits of the implementation of a real smart city programme, and showed how the proposed smart city energy model could be used for the planning of pilot projects. To the best of our knowledge, such a smart city energy model and modelling framework had not been developed and applied yet, and no economic results in terms of the potential benefits of such a smart city initiative had been previously reported.QC 20171010</p
Defect evolution during annealing of deformed FeSi alloys studied by positron annihilation spectroscopy
No full textHigh silicon steel is widely used in electrical appliances. Alloying iron with silicon improves its magnetic performance. A silicon content up to 6.5 wt. % gives excellent magnetic properties such as high saturation magnetization, near zero magnetostriction and low iron loss in high frequencies. Their workability is greatly reduced by the appearance of ordered structures, namely B2 and D03, as soon as the Si content becomes higher than 3.5 wt. %. This limits the mass production by conventional rolling to this maximum percentage of Si. In this work a series of FeSi (7.5 wt. % Si) samples with different degrees of deformation are investigated with positron annihilation spectroscopy and optical microscopy (OM). The influence of annealing on the concentration of defects of different deformed FeSi alloys has been investigated by positron annihilation lifetime spectroscopy and Doppler broadening of the annihilation radiation. OM is used to investigate the microstructure of deformed samples before and after annealing. The values of the S parameter present a decrease for all studied FeSi alloys with the increase of the annealing temperature, being attributed to a decrease of the concentration of defects. A sudden increase of the S-parameter value at 600?°C was observed for all samples, which could be related to the change of the ordering of the FeSi alloys at that temperature. At 700 °C, the values of the S parameter decreased drastically and starting from 900?°C, they became constant. The microstructures of the alloys, investigated by OM, show that recrystallization is completed at 900?°C and the samples are mainly free of defects, which is in agreement with the positron annihilation lifetime data.Materials Science and EngineeringMechanical, Maritime and Materials Engineerin
Influence of initial heating during final high temperature annealing on the offset of primary and secondary recrystallization in Cu-bearing grain oriented electrical steels
No full textThe industrial production route of Grain Oriented Electrical Steels (GOES) is complex and fine-tuned for each grade. Its metallurgical process requires in all cases the abnormal grain growth (AGG) of the Goss orientation during the final high temperature annealing (HTA). The exact mechanism of AGG is not yet fully understood, but is controlled by the different inhibition systems, namely MnS, AlN and CuxS, their size and distribution, and the initial primary recrystallized grain size. Therefore, among other parameters, the initial heating stage during the HTA is crucial for the proper development of primary and secondary recrystallized microstructures. Cold rolled 0.3 mm Cu-bearing Grain Oriented Electrical Steel has been submitted to interrupted annealing experiments in a lab tubular furnace. Two different annealing cycles were applied:• Constant heating at 30°C/h up to 1000°C. Two step cycle with initial heating at 100°C/h up to 600°C, followed by 18 h soaking at 600°C and then heating at 30°C/h up to 1050°C. The materials are analyzed in terms of their magnetic properties, grain size, texture and precipitates. The characteristic magnetic properties are analyzed for the different extraction temperatures and Cycles. As the annealing was progressing, the coercivity values (Hc 1.7T [A/m]) decreased, showing two abrupt drops, which can be associated to the on-set of primary and secondary recrystallization. The primary recrystallized grain sizes and recrystallized fractions are fitted to a model using a non-isothermal approach. This analysis shows that, although the resulting grain sizes were similar, the kinetics for the two step annealing were faster due to the lower recovery. The on-set of secondary recrystallization was also shifted to higher temperatures in the case of the continuous heating cycle, which might end in different final grain sizes and final magnetic properties. In both samples, nearly all the observed precipitates are Al-Si-Mn nitrides, ranging from pure AlN to Si4Mn-nitride
Influence of initial heating during final high temperature annealing on the offset of primary and secondary recrystallization in Cu-bearing grain oriented electrical steels
No full textEffect of silicon on the hot flow behavior of ultra-low carbon austenite
No full textThe influence of silicon on the high-temperature deformation behavior of ultra-low carbon austenite was studied in the range of temperature and strain rate from 1,000 to 1,100 degrees C and 0.001 to 0.1 s(-1), respectively. The flow curves of the steels exhibit the classic softening due to dynamic recrystallization. The characteristic pairs of stress-strain values (zero, critical, peak, saturation, and steady state) were determined by the analysis of the work hardening curves. These values were analyzed by applying first the classical Sellars and McTegart approach. Once the apparent stress exponents and activation energies were determined as being in the vicinity of 5 and above 270 kJ/mol, respectively, a modified hyperbolic sine equation was used. The flow curves were characterized by work hardening, dynamic recovery, and recrystallization terms at any processing conditions, showing a direct relationship with the silicon content of the steels. Finally, all the flow curves of studied steels were discussed and modeled as a function of the processing parameters and silicon content
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