Habermas, J., Teoría de la acción comunicativa.

Sin resume

Boladeras Cucurella, M., Razón crítica y sociedad.

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Optimal streaks in a Falkner-Skan boundary layer

This paper deals with the optimal streaky perturbations (which maximize the perturbed energy growth) in a wedge flow boundary layer. These three dimensional perturbations are governed by a system of linearized boundary layer equations around the Falkner-Skan base flow. Based on an asymptotic analysis of this system near the free stream and the leading edge singularity, we show that for acute wedge semi-angle, all solutions converge after a streamwise transient to a single streamwise-growing solution of the linearized equations, whose initial condition near the leading edge is given by an eigenvalue problem first formulated in this context by Tumin (2001). Such a solution may be regarded as a streamwise evolving most unstable streaky mode, in analogy with the usual eigenmodes in strictly parallel flows, and shows an approximate self-similarity, which was partially known and is completed in this paper. An important consequence of this result is that the optimization procedure based on the adjoint equations heretofore used to define optimal streaks is not necessary. Instead, a simple low-dimensional optimization process is proposed and used to obtain optimal streaks. Comparison with previous results by Tumin and Ashpis (2003) shows an excellent agreement. The unstable streaky mode exhibits transient growth if the wedge semi-angle is smaller than a critical value that is slightly larger than $\pi/6$, and decays otherwise. Thus the cases of right and obtuse wedge semi-angles exhibit less practical interest, but they show a qualitatively different behavior, which is briefly described to complete the analysis

Habermas, J., Teoría de la acción comunicativa.

Sin resume

A New Cutting Device Design to Study the Orthogonal Cutting of CFRP Laminates at Different Cutting Speeds

[EN] Carbon Fiber-reinforced plastics (CFRPs) are widely used in the aerospace industry due to their highly mechanical properties and low density. Most of these materials are used in high-risk structures, where the damage caused by machining must be controlled and minimized. The optimization of these processes is still a challenge in the industry. In this work, a special cutting device, which allows for orthogonal cutting tests, with a linear displacement at a wide range of constant cutting speeds, has been developed by the authors. This paper describes the developed cutting device and its application to analyze the influence of tool geometry and cutting parameters on the material damage caused by the orthogonal cutting of a thick multidirectional CFRP laminate. The results show that a more robust geometry (higher cutting edge radius and lower rake angle) and higher feed cause an increase in the thrust force of a cutting tool, causing burrs and delamination damage. By reducing the cutting speed, the components with a higher machining force were also observed to have less surface integrity control.This research was funded by the Ministry of economy, Industry and Competitiveness and FEDER (grant number: DPI2017-89197-C2-1-R).Criado, V.; Feito-Sánchez, N.; Cantero Guisández, J.; Díaz-Álvarez, J. (2019). A New Cutting Device Design to Study the Orthogonal Cutting of CFRP Laminates at Different Cutting Speeds. Materials. 12(24):1-13. https://doi.org/10.3390/ma12244074S1131224Che, D., Saxena, I., Han, P., Guo, P., & Ehmann, K. F. (2014). Machining of Carbon Fiber Reinforced Plastics/Polymers: A Literature Review. Journal of Manufacturing Science and Engineering, 136(3). doi:10.1115/1.4026526Vigneshwaran, S., Uthayakumar, M., & Arumugaprabu, V. (2018). Review on Machinability of Fiber Reinforced Polymers: A Drilling Approach. Silicon, 10(5), 2295-2305. doi:10.1007/s12633-018-9764-9Panchagnula, K. K., & Palaniyandi, K. (2018). Drilling on fiber reinforced polymer/nanopolymer composite laminates: a review. Journal of Materials Research and Technology, 7(2), 180-189. doi:10.1016/j.jmrt.2017.06.003Wang, F., Yin, J., Ma, J., & Niu, B. (2018). Heat partition in dry orthogonal cutting of unidirectional CFRP composite laminates. Composite Structures, 197, 28-38. doi:10.1016/j.compstruct.2018.05.040Fernández-Pérez, J., Cantero, J. L., Díaz-Álvarez, J., & Miguélez, M. H. (2017). Influence of cutting parameters on tool wear and hole quality in composite aerospace components drilling. Composite Structures, 178, 157-161. doi:10.1016/j.compstruct.2017.06.043Feito, N., Díaz-Álvarez, J., López-Puente, J., & Miguelez, M. H. (2018). Experimental and numerical analysis of step drill bit performance when drilling woven CFRPs. Composite Structures, 184, 1147-1155. doi:10.1016/j.compstruct.2017.10.061López de Lacalle, L. N., & Lamikiz, A. (2009). Milling of Carbon Fiber Reinforced Plastics. Advanced Materials Research, 83-86, 49-55. doi:10.4028/www.scientific.net/amr.83-86.49Feito, N., Diaz-Álvarez, A., Cantero, J. L., Rodríguez-Millán, M., & Miguélez, H. (2015). Experimental analysis of special tool geometries when drilling woven and multidirectional CFRPs. Journal of Reinforced Plastics and Composites, 35(1), 33-55. doi:10.1177/0731684415612931Henerichs, M., Voß, R., Kuster, F., & Wegener, K. (2015). Machining of carbon fiber reinforced plastics: Influence of tool geometry and fiber orientation on the machining forces. CIRP Journal of Manufacturing Science and Technology, 9, 136-145. doi:10.1016/j.cirpj.2014.11.002Yan, X., Reiner, J., Bacca, M., Altintas, Y., & Vaziri, R. (2019). A study of energy dissipating mechanisms in orthogonal cutting of UD-CFRP composites. Composite Structures, 220, 460-472. doi:10.1016/j.compstruct.2019.03.090Lopresto, V., Langella, A., Caprino, G., Durante, M., & Santo, L. (2017). Conventional Orthogonal Cutting Machining on Unidirectional Fibre Reinforced Plastics. Procedia CIRP, 62, 9-14. doi:10.1016/j.procir.2016.07.036Santiuste, C., Olmedo, A., Soldani, X., & Miguélez, H. (2012). Delamination prediction in orthogonal machining of carbon long fiber-reinforced polymer composites. Journal of Reinforced Plastics and Composites, 31(13), 875-885. doi:10.1177/0731684412444654ZITOUNE, R., COLLOMBET, F., LACHAUD, F., PIQUET, R., & PASQUET, P. (2005). Experiment?calculation comparison of the cutting conditions representative of the long fiber composite drilling phase. Composites Science and Technology, 65(3-4), 455-466. doi:10.1016/j.compscitech.2004.09.028Rao, G. V. G., Mahajan, P., & Bhatnagar, N. (2007). Micro-mechanical modeling of machining of FRP composites – Cutting force analysis. Composites Science and Technology, 67(3-4), 579-593. doi:10.1016/j.compscitech.2006.08.010Wang, H., Chang, L., Mai, Y.-W., Ye, L., & Williams, J. G. (2018). An experimental study of orthogonal cutting mechanisms for epoxies with two different crosslink densities. International Journal of Machine Tools and Manufacture, 124, 117-125. doi:10.1016/j.ijmachtools.2017.10.003Lopresto, V., Caggiano, A., & Teti, R. (2016). High Performance Cutting of Fibre Reinforced Plastic Composite Materials. Procedia CIRP, 46, 71-82. doi:10.1016/j.procir.2016.05.079Voss, R., Seeholzer, L., Kuster, F., & Wegener, K. (2019). Analytical force model for orthogonal machining of unidirectional carbon fibre reinforced polymers (CFRP) as a function of the fibre orientation. Journal of Materials Processing Technology, 263, 440-469. doi:10.1016/j.jmatprotec.2018.08.001Seeholzer, L., Voss, R., Grossenbacher, F., Kuster, F., & Wegener, K. (2018). Fundamental analysis of the cutting edge micro-geometry in orthogonal machining of unidirectional Carbon Fibre Reinforced Plastics (CFRP). Procedia CIRP, 77, 379-382. doi:10.1016/j.procir.2018.09.040Feito, N., Diaz-Álvarez, J., López-Puente, J., & Miguelez, M. H. (2016). Numerical analysis of the influence of tool wear and special cutting geometry when drilling woven CFRPs. Composite Structures, 138, 285-294. doi:10.1016/j.compstruct.2015.11.065Cepero-Mejías, F., Curiel-Sosa, J. L., Zhang, C., & Phadnis, V. A. (2019). Effect of cutter geometry on machining induced damage in orthogonal cutting of UD polymer composites: FE study. Composite Structures, 214, 439-450. doi:10.1016/j.compstruct.2019.02.012Santiuste, C., Soldani, X., & Miguélez, M. H. (2010). Machining FEM model of long fiber composites for aeronautical components. Composite Structures, 92(3), 691-698. doi:10.1016/j.compstruct.2009.09.021Soldani, X., Santiuste, C., Muñoz-Sánchez, A., & Miguélez, M. H. (2011). Influence of tool geometry and numerical parameters when modeling orthogonal cutting of LFRP composites. Composites Part A: Applied Science and Manufacturing, 42(9), 1205-1216. doi:10.1016/j.compositesa.2011.04.023Iliescu, D., Gehin, D., Iordanoff, I., Girot, F., & Gutiérrez, M. E. (2010). A discrete element method for the simulation of CFRP cutting. Composites Science and Technology, 70(1), 73-80. doi:10.1016/j.compscitech.2009.09.007Wang, D., He, X., Xu, Z., Jiao, W., Yang, F., Jiang, L., … Wang, R. (2017). Study on Damage Evaluation and Machinability of UD-CFRP for the Orthogonal Cutting Operation Using Scanning Acoustic Microscopy and the Finite Element Method. Materials, 10(2), 204. doi:10.3390/ma10020204Sahraie Jahromi, A., & Bahr, B. (2010). An analytical method for predicting cutting forces in orthogonal machining of unidirectional composites. Composites Science and Technology, 70(16), 2290-2297. doi:10.1016/j.compscitech.2010.09.005Wang, D. H., Ramulu, M., & Arola, D. (1995). Orthogonal cutting mechanisms of graphite/epoxy composite. Part I: unidirectional laminate. International Journal of Machine Tools and Manufacture, 35(12), 1623-1638. doi:10.1016/0890-6955(95)00014-oLi, H., Qin, X., He, G., Jin, Y., Sun, D., & Price, M. (2015). Investigation of chip formation and fracture toughness in orthogonal cutting of UD-CFRP. The International Journal of Advanced Manufacturing Technology, 82(5-8), 1079-1088. doi:10.1007/s00170-015-7471-xVoss, R., Seeholzer, L., Kuster, F., & Wegener, K. (2017). Influence of fibre orientation, tool geometry and process parameters on surface quality in milling of CFRP. CIRP Journal of Manufacturing Science and Technology, 18, 75-91. doi:10.1016/j.cirpj.2016.10.002Nayak, D., Bhatnagar, N., & Mahajan, P. (2005). MACHINING STUDIES OF UNI-DIRECTIONAL GLASS FIBER REINFORCED PLASTIC (UD-GFRP) COMPOSITES PART 1: EFFECT OF GEOMETRICAL AND PROCESS PARAMETERS. Machining Science and Technology, 9(4), 481-501. doi:10.1080/10910340500398167An, Q., Cai, C., Cai, X., & Chen, M. (2019). Experimental investigation on the cutting mechanism and surface generation in orthogonal cutting of UD-CFRP laminates. Composite Structures, 230, 111441. doi:10.1016/j.compstruct.2019.111441Bhatnagar, N., Nayak, D., Singh, I., Chouhan, H., & Mahajan, P. (2004). Determination of Machining-Induced Damage Characteristics of Fiber Reinforced Plastic Composite Laminates. Materials and Manufacturing Processes, 19(6), 1009-1023. doi:10.1081/amp-200035177Wang, X., Kwon, P. Y., Sturtevant, C., Kim, D. (Dae-W., & Lantrip, J. (2013). Tool wear of coated drills in drilling CFRP. Journal of Manufacturing Processes, 15(1), 127-135. doi:10.1016/j.jmapro.2012.09.019Fernández-Pérez, J., Cantero, J. L., Álvarez, J. D., & Miguélez, M. H. (2017). Composite Fiber Reinforced Plastic one-shoot drilling: Quality inspection assessment and tool wear evaluation. Procedia Manufacturing, 13, 139-145. doi:10.1016/j.promfg.2017.09.021Sorrentino, L., Turchetta, S., Colella, L., & Bellini, C. (2016). Analysis of Thermal Damage in FRP Drilling. Procedia Engineering, 167, 206-215. doi:10.1016/j.proeng.2016.11.689Díaz-Álvarez, J., Criado, V., Miguélez, H., & Cantero, J. (2018). PCBN Performance in High Speed Finishing Turning of Inconel 718. Metals, 8(8), 582. doi:10.3390/met8080582Su, Y. (2019). Effect of the cutting speed on the cutting mechanism in machining CFRP. Composite Structures, 220, 662-676. doi:10.1016/j.compstruct.2019.04.052Wang, X. M., & Zhang, L. C. (2003). An experimental investigation into the orthogonal cutting of unidirectional fibre reinforced plastics. International Journal of Machine Tools and Manufacture, 43(10), 1015-1022. doi:10.1016/s0890-6955(03)00090-7Xu, J., El Mansori, M., Voisin, J., Chen, M., & Ren, F. (2019). On the interpretation of drilling CFRP/Ti6Al4V stacks using the orthogonal cutting method: Chip removal mode and subsurface damage formation. Journal of Manufacturing Processes, 44, 435-447. doi:10.1016/j.jmapro.2019.05.05

Biocatalytic synthesis of oxygenated biofuels through the technologies of ionic liquids and supercritical carbon dioxide

Póster presentado en el Congreso Nacional de Biotecnologia (BIOTEC 2019), celebrado en Vigo (España) entre los días 10 y 13 de junio de 2019.The increase in the production of biofuels has generated in the market an excess of glycerol as a byproduct. Some glycerol derivatives, such as solketal (1,2-isopropylidene glycerol), have been used successfully to synthesize new oxygenated fuels, such as fatty acid solketal esters (FASE), in order to increase the octane number of the gasolines. Biodiesel exhibits an excellent suitability as a liquid fuel (adiabatic flame temperature, viscosity, etc.), blending up to 20% volume fraction of ASE

Escape dynamics in the discrete repulsive φ4 model

We study deterministic escape dynamics of the discrete Klein-Gordon model with a repulsive quartic on-site potential. Using a combination of analytical techniques, based on differential and algebraic inequalities and selected numerical illustrations, we first derive conditions for collapse of an initially excited single-site unit, for both the Hamiltonian and the linearly damped versions of the system and showcase different potential fates of the single-site excitation, such as the possibility to be "pulled back" from outside the well or to "drive over" the barrier some of its neighbors. Next, we study the evolution of a uniform (small) segment of the chain and, in turn, consider the conditions that support its escape and collapse of the chain. Finally, our path from one to the few and finally to the many excited sites is completed by a modulational stability analysis and the exploration of its connection to the escape process for plane wave initial data. This reveals the existence of three distinct regimes, namely modulational stability, modulational instability without escape and, finally, modulational instability accompanied by escape. These are corroborated by direct numerical simulations. In each of the above cases, the variations of the relevant model parameters enable a consideration of the interplay of discreteness and nonlinearity within the observed phenomenology. © 2012 Elsevier B.V. All rights reserved

Chemoselective Addition of Lithium Phosphides to Aldehydes and Epoxides in Deep Eutectic Solvents

Within the arsenal of organic synthesis, the chemistry of compounds of s-block elements (typically organolithium and Grignard reagents) has become one of the most useful tools to forge new C–C. Although a variety of synthetic methods has been developed so far to create C–N, C–O and C–S bonds, the number of protocols for the construction of new C–P connections is much more limited. Pioneering, independent studies from Hevia, García-Alvarez, and our own group have shown that the rate of alkylation/arylation of unsaturated functional groups (e.g., carbonyl compounds, imines, double bonds) by highly polar organometallic compounds successfully competes with protonation, when using environmentally responsible protic solvents like water and the so-called Deep Eutectic Solvents (DESs). In this communication, we wish to report that DESs can be used as environmentally friendly reaction media to promote a fast (within 3 s reaction time) and chemoselective addition of in-situ generated highly polarized lithium phosphides (LiPR2) to both aldehydes and epoxides, working at room temperature (RT) and under aerobic conditions, thereby granting access to α- and β-hydroxy-phosphine oxides, respectively, in very good yields (up to 94%)